Description
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.
No analysis available yet.
Remediation
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Tracking
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Advisories
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References
History
Fri, 04 Sep 2026 17:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | undici vulnerable to TLS certificate validation bypass via dropped connect options in BalancedPool | |
| Weaknesses | CWE-295 | |
| References |
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| Metrics |
cvssV3_1
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Subscriptions
No data.
Status: PUBLISHED
Assigner: openjs
Published:
Updated: 2026-09-04T18:37:44.620Z
Reserved: 2026-09-02T17:45:44.775Z
Link: CVE-2026-84961
No data.
Status : Received
Published: 2026-09-04T17:17:02.227
Modified: 2026-09-04T17:17:02.227
Link: CVE-2026-84961
No data.
OpenCVE Enrichment
No data.
Weaknesses
-
CWE-295
Improper Certificate Validation