undici WebSocket client vulnerable to denial of service via fragment count bypass (CVE-2026-12151)
Published Last modified Sources: Red Hat, BSI, SUSE, CVE.org, OSV, Hersteller
What is affected, what to do
A flaw was found in undici. A malicious WebSocket server can exploit this by streaming numerous small or empty continuation frames.
Update Undici to version 6.26.0, Undici to version 7.28.0, Undici to version 8.5.0.
- Affected
- Undici
lt *..6.26.0 - Undici
lt 7.0.0..7.28.0 - Undici
lt 8.0.0..8.5.0
- Undici
- Fixed in
- Undici
6.26.0 - Undici
7.28.0 - Undici
8.5.0
- Undici
Not sure whether and how you are affected? Ask a question about this vulnerability
Metrics
7.5
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
7.5
CVSS v3
Severity High on the scale from 0 to 10.
Source: Red Hat, BSI, SUSE, CVE.org, OSV, Hersteller
0.8 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 56.0
Show all metrics
- Severity
- High
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 81.77 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 7.5 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 7.5
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.8 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 56.0
- High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-400, CWE-770
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
A flaw was found in undici. A malicious WebSocket server can exploit this by streaming numerous small or empty continuation frames. This can bypass per-frame and cumulative-size validation, leading to unbounded memory growth in the client process. The primary consequence is memory exhaustion, resulting in a denial of service (DoS) for affected applications using the undici WebSocket client or WebSocketStream API.
Source: redhat_csaf, BSI WID Portal, BSI CSAF, suse_csaf, cvelistv5, OSV (Open Source Vulnerabilities), NVD (NIST), GitHub Security Advisories
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| undici | undici |
|
|
| nodejs | undici |
|
|
| IBM | App Connect Enterprise |
|
|
| IBM | App Connect Enterprise CD |
|
|
| IBM | App Connect Enterprise LTS |
|
|
| npm | undici |
|
|
Vendors and products
Weakness classes (CWE)
CWE-400Uncontrolled Resource Consumption
Class
The product does not properly control the allocation and maintenance of a limited resource.
Entry at MITRE CWE-400CWE-770Allocation of Resources Without Limits or Throttling
Base
The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.
Entry at MITRE CWE-770
References & sources
- github.comnodejs/undici/security/advisories/GHSA-vxpw-j846-p89qweb
- NVD (NIST)vuln/detail/CVE-2026-12151advisory
- cna.openjsf.orgsecurity-advisories.htmlweb
- github.comnodejs/undicipackage
- access.redhat.comsecurity/cve/CVE-2026-12151Vulnerability database, x_refsource_REDHAT
- bugzilla.redhat.comRHBZ#2489980Issue tracking, x_refsource_REDHAT
- security.access.redhat.comdata/csaf/v2/vex/2026/cve-2026-12151.jsonx_sadp-csaf-vex
- access.redhat.comerrata/RHSA-2026:48151Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:39246Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:35842Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:35841Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:41947Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:39868Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:35892Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:35891Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:34342Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:36754Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:41929Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:38236Vendor advisory, x_refsource_REDHAT
- access.redhat.comerrata/RHSA-2026:38009Vendor advisory, x_refsource_REDHAT
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
Record modifiedRed Hat ADP
Show 3 original changes
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12151.json">CVE-2026-12151</a>Reference added —https://access.redhat.com/errata/RHSA-2026:66488Reference added —https://access.redhat.com/errata/RHSA-2026:66545Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
1 individual change: Affected versions (publisher)
Show the original change
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12151.json">CVE-2026-12151</a>Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
New references:Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12151.json">CVE-2026-12151</a>Reference added —https://access.redhat.com/errata/RHSA-2026:65126Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
1 individual change: Affected versions (publisher)
Show the original change
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12151.json">CVE-2026-12151</a>Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedOpenJS Foundation
Show 6 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://cna.openjsf.org/security-advisories.htmlReference added —https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89qReference removed https://cna.openjsf.org/security-advisories.html—Reference removed https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89q—Reference type removed https://cna.openjsf.org/security-advisories.html Types: Vendor Advisory—Reference type removed https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89q Types: Vendor Advisory—Source identifier: ce714d77-add3-4f53-aff5-83d477b104bb
Show 13 older changes
Record modifiedRed Hat ADP
Show 50 original changes
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/12xxx/CVE-2026-12151.json">CVE-2026-12151</a>Reference added —https://access.redhat.com/errata/RHSA-2026:34342Reference added —https://access.redhat.com/errata/RHSA-2026:35841Reference added —https://access.redhat.com/errata/RHSA-2026:35842Reference added —https://access.redhat.com/errata/RHSA-2026:35891Reference added —https://access.redhat.com/errata/RHSA-2026:35892Reference added —https://access.redhat.com/errata/RHSA-2026:36621Reference added —https://access.redhat.com/errata/RHSA-2026:36754Reference added —https://access.redhat.com/errata/RHSA-2026:36820Reference added —https://access.redhat.com/errata/RHSA-2026:38009Reference added —https://access.redhat.com/errata/RHSA-2026:38236Reference added —https://access.redhat.com/errata/RHSA-2026:39246Reference added —https://access.redhat.com/errata/RHSA-2026:39868Reference added —https://access.redhat.com/errata/RHSA-2026:41929Reference added —https://access.redhat.com/errata/RHSA-2026:41947Reference added —https://access.redhat.com/errata/RHSA-2026:47728Reference added —https://access.redhat.com/errata/RHSA-2026:48124Reference added —https://access.redhat.com/errata/RHSA-2026:48151Reference added —https://access.redhat.com/errata/RHSA-2026:52399Reference added —https://access.redhat.com/errata/RHSA-2026:56366Reference added —https://access.redhat.com/errata/RHSA-2026:56431Reference added —https://access.redhat.com/errata/RHSA-2026:57013Reference added —https://access.redhat.com/errata/RHSA-2026:60520Reference added —https://access.redhat.com/security/cve/CVE-2026-12151Reference added —https://bugzilla.redhat.com/show_bug.cgi?id=2489980Reference added —https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12151.jsonReference removed https://access.redhat.com/errata/RHSA-2026:34342—Reference removed https://access.redhat.com/errata/RHSA-2026:35841—Reference removed https://access.redhat.com/errata/RHSA-2026:35842—Reference removed https://access.redhat.com/errata/RHSA-2026:35891—Reference removed https://access.redhat.com/errata/RHSA-2026:35892—Reference removed https://access.redhat.com/errata/RHSA-2026:36621—Reference removed https://access.redhat.com/errata/RHSA-2026:36754—Reference removed https://access.redhat.com/errata/RHSA-2026:36820—Reference removed https://access.redhat.com/errata/RHSA-2026:38009—Reference removed https://access.redhat.com/errata/RHSA-2026:38236—Reference removed https://access.redhat.com/errata/RHSA-2026:39246—Reference removed https://access.redhat.com/errata/RHSA-2026:39868—Reference removed https://access.redhat.com/errata/RHSA-2026:41929—Reference removed https://access.redhat.com/errata/RHSA-2026:41947—Reference removed https://access.redhat.com/errata/RHSA-2026:47728—Reference removed https://access.redhat.com/errata/RHSA-2026:48124—Reference removed https://access.redhat.com/errata/RHSA-2026:48151—Reference removed https://access.redhat.com/errata/RHSA-2026:52399—Reference removed https://access.redhat.com/errata/RHSA-2026:56366—Reference removed https://access.redhat.com/errata/RHSA-2026:56431—Reference removed https://access.redhat.com/errata/RHSA-2026:57013—Reference removed https://access.redhat.com/security/cve/CVE-2026-12151—Reference removed https://bugzilla.redhat.com/show_bug.cgi?id=2489980—Reference removed https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12151.json—Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
1 individual change: Affected versions (publisher)
Show the original change
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) changed Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+111)Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+111)Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
New references:Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://access.redhat.com/errata/RHSA-2026:57013Affected versions (publisher) changed Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+89)Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+111)Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
Show 3 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://access.redhat.com/errata/RHSA-2026:56366Reference added —https://access.redhat.com/errata/RHSA-2026:56431Affected versions (publisher) changed Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+53)Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+89)Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
New references:Show the original change
Individual changes of this event as published by NVD Type Action Before After Reference added —https://access.redhat.com/errata/RHSA-2026:52399Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
New references:Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://access.redhat.com/errata/RHSA-2026:47728Affected versions (publisher) changed Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+51)Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+52)Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
Show 3 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://access.redhat.com/errata/RHSA-2026:48124Reference added —https://access.redhat.com/errata/RHSA-2026:48151Affected versions (publisher) changed Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support (+51)Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10 (+51)Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
Show 3 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://access.redhat.com/errata/RHSA-2026:41929Reference added —https://access.redhat.com/errata/RHSA-2026:41947Affected versions (publisher) changed Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support (+50)Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support (+51)Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
Show 3 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://access.redhat.com/errata/RHSA-2026:36754Reference added —https://access.redhat.com/errata/RHSA-2026:36820Affected versions (publisher) changed Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux AppStream (v. 9), Cluster Observability Operator 1.5.0 (+12)Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux AppStream (v. 9), Cluster Observability Operator 1.5.0 (+13)Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Record modifiedRed Hat ADP
Show 3 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://access.redhat.com/errata/RHSA-2026:35841Reference added —https://access.redhat.com/errata/RHSA-2026:35842Affected versions (publisher) changed Cluster Observability Operator 1.5.0, Cryostat 4, OpenShift Pipelines (+12)Red Hat Enterprise Linux AppStream (v. 10), Cluster Observability Operator 1.5.0, Cryostat 4 (+12)Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Initial analysis by NVDNVD
Newly listed as affected:- Nodejs undici (8.0.0 – before 8.5.0; 7.0.0 – before 7.28.0; 6.17.0 – before 6.27.0)
Show 3 original changes
Individual changes of this event as published by NVD Type Action Before After Product configuration added —OR *cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* versions from (including) 8.0.0 up to (excluding) 8.5.0 *cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* versions from (including) 7.0.0 up to (excluding) 7.28.0 *cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* versions from (including) 6.17.0 up to (excluding) 6.27.0Reference type added —openjs: https://cna.openjsf.org/security-advisories.html Types: Vendor AdvisoryReference type added —openjs: https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89q Types: Vendor AdvisorySource identifier: nvd@nist.gov
Record modifiedCISA ADP
CISA assessment (SSVC): exploitation: none known, automatable: yes
Show the original change
Individual changes of this event as published by NVD Type Action Before After SSVC assessment added —{"id":"CVE-2026-12151","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-06-17T17:29:57.305732Z"}Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
ReceivedOpenJS Foundation
CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness type: CWE-400, CWE-770
Description added or changed
Show 7 original changes
Individual changes of this event as published by NVD Type Action Before After Affected versions (publisher) added —undiciDescription added —Impact: The undici WebSocket client enforces maxPayloadSize on the cumulative byte count of fragments in a message but does not enforce a limit on the number of fragments. A malicious WebSocket server can stream many small or empty continuation frames that each pass per-frame and cumulative-size validation, collectively causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service. Affected applications are those using the undici WebSocket client (new WebSocket(...)) or the WebSocketStream API that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint. All releases starting at undici 6.17.0 are affected. Patches: Upgrade to undici >= 6.26.0, >= 7.28.0, or >= 8.5.0. Workarounds: No workaround is available. The fix must be applied through an upgrade.CVSS added —AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HWeakness type (CWE) added —CWE-400Weakness type (CWE) added —CWE-770Reference added —https://cna.openjsf.org/security-advisories.htmlReference added —https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89qSource identifier: ce714d77-add3-4f53-aff5-83d477b104bb
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-12151"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-12151.svg?lang=en" alt="CVE-2026-12151 – NEOSEC Intel" height="20"></a>