CVE-2026-84961

undici's BalancedPool constructor passes its entire options object through an internal deep-clone that serializes and reparses the value as JSON. Because JSON cannot represent functions, any function-valued TLS option, such as a caller-supplied checkServerIdentity callback or a custom connector inside the connect option, is silently discarded before it reaches the TLS layer. As a result a peer whose certificate the application's custom checkServerIdentity was written to reject, but which still passes Node's default hostname and chain checks, is accepted when reached through BalancedPool. The Client, Pool, and Agent dispatchers are not affected because they extract the connect and tls options before cloning. This affects undici versions from 7.24.1 up to 7.29.1 and from 8.0.0 up to 8.10.2, and only when the application supplies a function-valued connect or tls option to BalancedPool. Users should upgrade to undici 7.29.1 or 8.10.2.

CVSS v3 7.4 HIGH

7.4^/10

CVSS v3 : HIGH

Vector :

Exploitability : 2.2 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://cna.openjsf.org/security-advisories.html	Third Party Advisory
https://github.com/nodejs/undici/security/advisories/GHSA-w293-vg96-wgc3	Mitigation Vendor Advisory

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:nodejs:undici::::::node.js::*
	cpe:2.3:a:nodejs:undici::::::node.js::*

History

No history.

Information

Published : 2026-09-04 17:17

Updated : 2026-09-15 14:29

NVD link : CVE-2026-84961

Mitre link : CVE-2026-84961

CVE.ORG link : CVE-2026-84961

JSON object : View

Products Affected

nodejs

undici

CWE

CWE-295

Improper Certificate Validation

{"id": "CVE-2026-84961", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-84961", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "version": "2.0.3", "timestamp": "2026-09-04T18:35:57.858790Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "ce714d77-add3-4f53-aff5-83d477b104bb", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.4, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}, "impactScore": 5.2, "exploitabilityScore": 2.2}, {"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 9.1, "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}, "impactScore": 5.2, "exploitabilityScore": 3.9}]}, "affected": [{"source": "ce714d77-add3-4f53-aff5-83d477b104bb", "affectedData": [{"vendor": "undici", "product": "undici", "versions": [{"status": "affected", "version": "7.24.1", "lessThan": "7.29.1", "versionType": "semver"}, {"status": "unaffected", "version": "7.29.1", "versionType": "semver"}, {"status": "affected", "version": "8.0.0", "lessThan": "8.10.2", "versionType": "semver"}, {"status": "unaffected", "version": "8.10.2", "versionType": "semver"}], "packageURL": "pkg:npm/undici", "defaultStatus": "unaffected"}]}], "published": "2026-09-04T17:17:02.227", "references": [{"url": "https://cna.openjsf.org/security-advisories.html", "tags": ["Third Party Advisory"], "source": "ce714d77-add3-4f53-aff5-83d477b104bb"}, {"url": "https://github.com/nodejs/undici/security/advisories/GHSA-w293-vg96-wgc3", "tags": ["Mitigation", "Vendor Advisory"], "source": "ce714d77-add3-4f53-aff5-83d477b104bb"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "ce714d77-add3-4f53-aff5-83d477b104bb", "description": [{"lang": "en", "value": "CWE-295"}]}], "descriptions": [{"lang": "en", "value": "undici's BalancedPool constructor passes its entire options object through an internal deep-clone that serializes and reparses the value as JSON. Because JSON cannot represent functions, any function-valued TLS option, such as a caller-supplied checkServerIdentity callback or a custom connector inside the connect option, is silently discarded before it reaches the TLS layer. As a result a peer whose certificate the application's custom checkServerIdentity was written to reject, but which still passes Node's default hostname and chain checks, is accepted when reached through BalancedPool. The Client, Pool, and Agent dispatchers are not affected because they extract the connect and tls options before cloning. This affects undici versions from 7.24.1 up to 7.29.1 and from 8.0.0 up to 8.10.2, and only when the application supplies a function-valued connect or tls option to BalancedPool. Users should upgrade to undici 7.29.1 or 8.10.2."}], "lastModified": "2026-09-15T14:29:35.253", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:*", "vulnerable": true, "matchCriteriaId": "14C3FEF7-6460-4986-8FEB-A9F8540F14BA", "versionEndExcluding": "7.29.1", "versionStartIncluding": "7.24.1"}, {"criteria": "cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:*", "vulnerable": true, "matchCriteriaId": "848B6624-1708-4BF8-B9D7-8F34343D244B", "versionEndExcluding": "8.10.2", "versionStartIncluding": "8.0.0"}], "operator": "OR"}]}], "sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb"}