GHSA-vmh5-mc38-953g CVE-2026-9697

undici vulnerable to TLS certificate validation bypass via dropped requestTls in SOCKS5 ProxyAgent

High npm

Severity: 7.4 / 10; High · CVSS 3.1
Exploit chance (EPSS): 0.46%; Chance of exploitation in the next 30 days. Higher than 39.77% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-295 Improper Certificate Validation
Fix: 7.28.0; Upgrade undici to this version or later

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.

Affected versions

npm

Package	Vulnerable	Fixed in
undici	`>= 7.23.0, < 7.28.0`	`7.28.0`
undici	`>= 8.0.0, < 8.5.0`	`8.5.0`
undici	`>= 7.23.0, < 7.28.0`	`7.28.0`
undici	`>= 8.0.0, < 8.5.0`	`8.5.0`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

undici npm → `7.28.0`

npm

npm install undici@7.28.0

yarn

yarn add undici@7.28.0

pnpm

pnpm add undici@7.28.0

Severity breakdown

CVSS 3.1 7.4

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack vector: Network
Attack complexity: High
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: None

Weakness

CWE-295: Improper Certificate Validation

The product does not validate, or incorrectly validates, a certificate.

How to prevent it

Architecture and Design, Implementation: Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
Implementation: If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.

References

Advisories

Packages

github.com/nodejs/undici

Timeline

Jun 17, 2026 Published
Sep 10, 2026 Last updated by the source
Nov 1, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-55wc-3pg8-jfw6 undici vulnerable to Denial of Service via unhandled exception in the decompress interceptor	High	Also affects undici
GHSA-qrxm-fqhp-jwvm undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation	High	Also affects undici
GHSA-9fm3-97px-rjf6 undici WebSocket client vulnerable to Denial of Service via unbounded automatic PONG buffering	High	Also affects undici
GHSA-4qv8-2p9j-2685 undici vulnerable to Denial of Service via unbounded memory in the EventSource parser	High	Also affects undici
GHSA-xjj6-f33q-929c undici vulnerable to Denial of Service via unhandled error on excessive content-encodings	High	Also affects undici
GHSA-f72v-6w45-q472 undici vulnerable to Subresource Integrity bypass via non-lowercase algorithm tokens	High	Also affects undici
GHSA-4w7w-5xrc-9h26 undici vulnerable to cache poisoning and cross-user disclosure via cross-origin redirects	Critical	Also affects undici
GHSA-2m5v-pch6-74hx undici vulnerable to TLS certificate validation bypass via dropped tls options in Agent	Critical	Also affects undici

Credits: UlisesGascon, tonghuaroot

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