GitHub Advisoryadvisory · npm

GHSA-vmh5-mc38-953g undici vulnerable to TLS certificate validation bypass via dropped requestTls in SOCKS5 ProxyAgent

HIGH Published 2026-06-18 Modified 2026-06-18 Official page ↗
Aliases
CVE-2026-9697
Ecosystem
npm
Packages
undici
Severity
High
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weaknesses
CWE-295
Reviewed
2026-06-18

Affected packages

• npm undici: >= 7.23.0, < 7.28.0 → fixed in 7.28.0 • npm undici: >= 8.0.0, < 8.5.0 → fixed in 8.5.0

Description

Impact undici's `ProxyAgent` silently drops the `requestTls` option when configured with a SOCKS5 proxy URI (`socks5://` or `socks://`). The target HTTPS connection through the SOCKS5 tunnel falls back to Node's default trust store, ignoring user-configured `ca`, `cert`, `key`, `rejectUnauthorized`, and `servername` settings. Applications that pin to an internal or corporate CA via `requestTls.ca` will, when their proxy URI is SOCKS5, get the default Mozilla CA bundle as the trust anchor instead. Any cert signed by any publicly-trusted CA for the target hostname is accepted, breaking the intended pin and enabling MITM read and tamper of the HTTPS exchange. Affected applications are those that use undici's `ProxyAgent` (or `Socks5ProxyAgent` directly) with SOCKS5 AND rely on `requestTls` for TLS scope restriction. The bug was introduced in undici 7.23.0 when SOCKS5 support was added. Patches Upgrade to undici v7.28.0 or v8.5.0. Workarounds No workaround is available within the SOCKS5 path. If a SOCKS5 proxy with TLS scope restriction is required and an upgrade is not yet possible, route the traffic through an HTTP-proxy `ProxyAgent` instead, where `requestTls` is honored correctly.

Related

Alias · CVE (1)

  • CVE-2026-9697 Impact: undici's ProxyAgent silently drops the requestTls option when configured with a SOCKS5 proxy URI (socks5:// or socks://). vulnerability

Weakness · CWE (1)

  • CWE-295 Improper Certificate Validation weakness

References