undici up to 7.29.0/8.10.1 BalancedPool BalancedPool constructor connect/tls certificate validation

Summaryinfo

A vulnerability described as problematic has been identified in undici up to 7.29.0/8.10.1. This affects the function BalancedPool constructor of the component BalancedPool. Executing a manipulation of the argument connect/tls can lead to certificate validation. This vulnerability is tracked as CVE-2026-84961. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability has been found in undici up to 7.29.0/8.10.1 and classified as problematic. This vulnerability affects the function BalancedPool constructor of the component BalancedPool. The manipulation of the argument connect/tls with an unknown input leads to a certificate validation vulnerability. The CWE definition for the vulnerability is CWE-295. The product does not validate, or incorrectly validates, a certificate. As an impact it is known to affect integrity. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability was named CVE-2026-84961 since 09/02/2026. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1587.003 by the MITRE ATT&CK project.

Upgrading to version 7.29.1 or 8.10.2 eliminates this vulnerability.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Name

• undici

Version

• 7.0
• 7.1
• 7.2
• 7.3
• 7.4
• 7.5
• 7.6
• 7.7
• 7.8
• 7.9
• 7.10
• 7.11
• 7.12
• 7.13
• 7.14
• 7.15
• 7.16
• 7.17
• 7.18
• 7.19
• 7.20
• 7.21
• 7.22
• 7.23
• 7.24
• 7.25
• 7.26
• 7.27
• 7.28
• 7.29.0
• 8.10.0
• 8.10.1

CPE 2.3info

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CPE 2.2info

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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