undici vulnerable to Denial of Service via unbounded memory in the EventSource parser (CVE-2026-109924)

What is affected, what to do

A flaw was found in undici. A malicious server can trigger a Denial of Service (DoS) by exhausting application memory.

Update Undici to version 6.29.1, Undici to version 7.30.1, Undici to version 8.12.2.

Affected

• Undici lt 6.5.0..6.29.1
• Undici lt 7.0.0..7.30.1
• Undici lt 8.0.0..8.12.2

Fixed in

• Undici 6.29.1
• Undici 7.30.1
• Undici 8.12.2

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

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 server can trigger a Denial of Service (DoS) by exhausting application memory. When an application connects to an untrusted Server-Sent Events (SSE) feed, the EventSource parser does not properly limit retained internal state when processing fragmented lines or repeated message fields. This allows an attacker to send crafted or compressed responses that consume excessive memory and terminate the application process.

Source: redhat_csaf, OSV (Open Source Vulnerabilities), GitHub Security Advisories, NVD (NIST), cvelistv5

Vendors and products

• NodeJS Nodejs undici
• Undici Undici

Weakness classes (CWE)

• CWE-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-4qv8-2p9j-2685Vendor advisory, web
• cna.openjsf.orgsecurity-advisories.htmlVendor advisory, web
• NVD (NIST)vuln/detail/CVE-2026-109924advisory
• github.comnodejs/undici/commit/299162740d5f39120092277e70efacb4d151c1c6web
• github.comnodejs/undici/commit/789ef26461c648480433846607154f52d74ec9abweb
• github.comnodejs/undici/commit/c43b23fdc6b37e1283d4347408bb16800f867d9eweb
• github.comnodejs/undicipackage
• github.comnodejs/undici/releases/tag/v6.29.1web
• github.comnodejs/undici/releases/tag/v7.30.1web
• github.comnodejs/undici/releases/tag/v8.12.2web

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).

1. 19.10.2026Initial analysis by NVDNVD

   Newly listed as affected:

   • Nodejs undici (7.0.0 – before 7.30.1; 8.0.0 – before 8.12.2; 6.5.0 – before 6.29.1)

   CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

   New references:

   • https://cna.openjsf.org/security-advisories.html
   • https://github.com/nodejs/undici/security/advisories/GHSA-4qv8-2p9j-2685
   Show 4 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   CVSS	added	—	AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
   Product configuration	added	—	OR *cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* versions from (including) 7.0.0 up to (excluding) 7.30.1 *cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* versions from (including) 8.0.0 up to (excluding) 8.12.2 *cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* versions from (including) 6.5.0 up to (excluding) 6.29.1
   Reference type	added	—	openjs: https://cna.openjsf.org/security-advisories.html Types: Vendor Advisory
   Reference type	added	—	openjs: https://github.com/nodejs/undici/security/advisories/GHSA-4qv8-2p9j-2685 Types: Vendor Advisory

   Source identifier: nvd@nist.gov

2. 16.10.2026Record modifiedCISA ADP

   CISA assessment (SSVC): exploitation: none known, automatable: no

   Show the original change

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   SSVC assessment	added	—	{"id":"CVE-2026-109924","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T20:05:08.940657Z"}

   Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

3. 15.10.2026ReceivedOpenJS Foundation

   CVSS V3.1: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

   Weakness type: CWE-770

   Description added or changed

   New references:

   • https://cna.openjsf.org/security-advisories.html
   • https://github.com/nodejs/undici/security/advisories/GHSA-4qv8-2p9j-2685
   Show 6 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Description	added	—	undici is an HTTP client library for Node.js. In versions 6.5.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, its EventSource client can be driven to exhaust process memory by a malicious or compromised Server-Sent Events peer. By sending millions of tiny completed data fields with no blank event separator, or a single unfinished line split across many chunks, the parser retains a growing amount of per-field and per-chunk state that the byte-based maxEventSize and maxResponseSize limits do not bound, and because maxResponseSize is enforced on the compressed body before decompression, a small compressed response can expand into enough retained memory to terminate the process. An application only needs to maintain an EventSource connection to an untrusted peer, which controls only the response, and availability is the only impact. The issue is fixed in undici 6.29.1, 7.30.1, and 8.12.2, which bound the retained parser state independently of the byte limits, and users should upgrade to one of those versions or later. There is no workaround.
   CVSS	added	—	AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
   Weakness type (CWE)	added	—	CWE-770
   Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/109xxx/CVE-2026-109924.json">CVE-2026-109924</a>
   Reference	added	—	https://cna.openjsf.org/security-advisories.html
   Reference	added	—	https://github.com/nodejs/undici/security/advisories/GHSA-4qv8-2p9j-2685

   Source identifier: ce714d77-add3-4f53-aff5-83d477b104bb