CVE-2026-84961 (GCVE-0-2026-84961)

Vulnerability from cvelistv5 – Published: 2026-09-04 16:47 – Updated: 2026-09-04 18:37
VLAI
Title
undici vulnerable to TLS certificate validation bypass via dropped connect options in BalancedPool
Summary
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.
Severity
7.4 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-04 18:35 UTC
CWE
  • CWE-295 - Improper Certificate Validation
Assigner
openjs CNA under the redhat root
CNA scorecard C 65/100 over 119 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
undici undici Affected: 7.24.1 , < 7.29.1 (semver)
Unaffected: 7.29.1 (semver)
Affected: 8.0.0 , < 8.10.2 (semver)
Unaffected: 8.10.2 (semver)
guessed Create a notification for this product.
Credits
MegaManSec mcollina UlisesGascon
Show details on NVD website
To clipboard 

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