CVE-2026-9697 undici vulnerable to TLS certificate validation bypass via dropped requestTls in SOCKS5 ProxyAgent
Attackers can perform man-in-the-middle attacks on HTTPS traffic routed through SOCKS5 proxies by bypassing custom TLS certificate validation settings in undici.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-9697?
CVE-2026-9697 is a high-severity vulnerability in Nodejs Undici, published on 17 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-295
Which versions are affected by CVE-2026-9697?
4 open source packages ship an affected version, including undici. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
undici npm | From 7.23.0 | 7.28.0 |
undici npm | From 7.23.0 | 7.28.0 |
undici npm | From 8.0.0 | 8.5.0 |
undici npm | From 8.0.0 | 8.5.0 |
Products include Nodejs Undici.
How do I fix CVE-2026-9697?
Upgrade undici to a fixed version for your release line: 7.28.0 or 8.5.0.
Is CVE-2026-9697 being exploited?
There is no known exploitation of CVE-2026-9697 in the wild and no public exploit code.
Other vulnerabilities in Nodejs Undici
- CVE-2026-109855 undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake
- CVE-2026-109869 undici vulnerable to Denial of Service via unhandled error on excessive content-encodings
- CVE-2026-87018 undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation
- CVE-2026-19534 undici vulnerable to Denial of Service via unrequested WebSocket subprotocol
- CVE-2026-12151 undici WebSocket client vulnerable to denial of service via fragment count bypass
Sources
Also known as AZL-91227, DEBIAN-CVE-2026-9697, ECHO-b305-6c79-97eb, GHSA-vmh5-mc38-953g, MINI-7cj7-6cr6-r892, MINI-8xv9-p578-x7w8 and 6 more.