undici vulnerable to TLS certificate validation bypass via dropped tls options in Agent (CVE-2026-109383)

What is affected, what to do

A flaw was found in undici. This vulnerability may allow a remote attacker to intercept or modify encrypted communications by bypassing custom certificate validation.

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

Affected

• Undici lt 4.0.0..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. This vulnerability may allow a remote attacker to intercept or modify encrypted communications by bypassing custom certificate validation. The issue occurs because the Agent dispatcher discards caller-supplied Transport Layer Security (TLS) verification functions during internal configuration copying, causing the client to silently ignore application-specific checks such as certificate or public-key pinning.

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

Vendors and products

• NodeJS Nodejs undici
• Undici Undici

Weakness classes (CWE)

• CWE-295Improper Certificate Validation

  Base

  The product does not validate, or incorrectly validates, a certificate.

  Entry at MITRE CWE-295

References & sources

• github.comnodejs/undici/security/advisories/GHSA-2m5v-pch6-74hxMitigation, Vendor advisory, web
• cna.openjsf.orgsecurity-advisories.htmlVendor advisory, web
• NVD (NIST)vuln/detail/CVE-2026-109383advisory
• github.comnodejs/undici/commit/04cb74b1db131ff8f5b4557dce811cbf5f4664b4web
• github.comnodejs/undici/commit/8c59f6b302898cb2e9b0f7962cd7212b6e597c9fweb
• github.comnodejs/undici/commit/f75eac00ac177f7b2e6c8bfbd52d4113164286e6web
• 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; 4.0.0 – before 6.29.1)

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

   New references:

   • https://cna.openjsf.org/security-advisories.html
   • https://github.com/nodejs/undici/security/advisories/GHSA-2m5v-pch6-74hx
   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:H/I:H/A:N
   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) 4.0.0 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-2m5v-pch6-74hx Types: Mitigation, 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-2026-109383","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T20:03:13.245340Z"}

   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:H/I:H/A:N

   Weakness type: CWE-295

   Description added or changed

   New references:

   • https://cna.openjsf.org/security-advisories.html
   • https://github.com/nodejs/undici/security/advisories/GHSA-2m5v-pch6-74hx
   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 4.0.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, its Agent dispatcher passes its constructor options through a JSON-based deep clone before forwarding them to each per-origin pool, and because JSON cannot represent functions, a caller-supplied tls option containing a checkServerIdentity callback is silently dropped before it reaches the TLS layer. As a result, a TLS peer whose certificate a custom checkServerIdentity was written to reject, but which passes Node's default hostname and chain checks, is silently accepted. Because Agent is the default dispatcher behind request, fetch, and setGlobalDispatcher, this affects the path most applications use, and EnvHttpProxyAgent is affected on its direct and no-proxy routes as well, while only applications that pass a function-valued tls option such as a custom checkServerIdentity for certificate or public-key pinning are at risk. The issue is fixed in undici 6.29.1, 7.30.1, and 8.12.2, which preserve the tls option outside the JSON clone so custom verification callbacks are forwarded unchanged, and users should upgrade to one of those versions or later. As a workaround, pass the TLS options through connect instead of tls, or for proxied destinations use requestTls and proxyTls.
   CVSS	added	—	AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
   Weakness type (CWE)	added	—	CWE-295
   Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/109xxx/CVE-2026-109383.json">CVE-2026-109383</a>
   Reference	added	—	https://cna.openjsf.org/security-advisories.html
   Reference	added	—	https://github.com/nodejs/undici/security/advisories/GHSA-2m5v-pch6-74hx

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