CVE-2026-84961undici vulnerable to TLS certificate validation bypass via dropped connect options in BalancedPool
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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
- 7.4 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- Weakness (CWE)
- CWE-295
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- openjs
- NVD analysis
- Analyzed
- Record last updated
- Sep 4, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
undici undici undici:undici (from the name) | from 7.24.1 before 7.29.1; 7.29.1 not affected; from 8.0.0 before 8.10.2; 8.10.2 not affected | CNA record |
nodejs undici nodejs:undici | from 7.24.1 before 7.29.1; from 8.0.0 before 8.10.2 | NVD |
References
- https://github.com/nodejs/undici/security/advisories/GHSA-w293-vg96-wgc3mitigation, vendor-advisory
- https://cna.openjsf.org/security-advisories.htmlthird-party-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.