undici vulnerable to TLS certificate validation bypass via dropped requestTls in SOCKS5 ProxyAgent
Published 18 Jun 2026 · Updated 10 Sept 2026
Affected packages
- Affected
- >=7.23.0 <7.28.0
- Fixed in
- 7.28.0
npm install undici@7.28.0- Affected
- >=8.0.0 <8.5.0
- Fixed in
- 8.5.0
npm install undici@8.5.0Details
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.
Is GHSA-vmh5-mc38-953g in any of your client repos?
Checking one package by hand is fine. Checking it across forty client projects is not. NPMscan reads the lockfiles in every GitHub repo you pick, finds each project with an affected undici, and gives you the command that fixes it.
References
Advisory data from OSV.dev (opens OSV.dev in a new tab), refreshed daily.