🛡️ CVE-2026-16729 — undici

🟡 CVSS 4.8 — Medium ✅ No Known Exploit CWE-74 OSV

4.8

CVSS Score

0 Low4 Medium7 High9 Critical10

Description

undici vulnerable to cookie attribute injection via unsanitized domain and unparsed setCookie fields

Impact

The setCookie function has two attribute injection paths. validateCookieDomain does not reject semicolons (validateCookiePath already does at 0x3B), so a domain value like example.com; SameSite=None lands verbatim as Domain=example.com; SameSite=None. The unparsed array's loop only checks each entry contains = and does not sanitize values, so an entry like X-Custom=val; HttpOnly lands unchanged, injecting HttpOnly without the caller setting cookie.httpOnly = true.

Applications that pass user-controlled input to these fields, typically multi-tenant or reverse-proxy servers that scope session cookies to a tenant-supplied domain, can have SameSite CSRF protections bypassed, Secure or HttpOnly forced or stripped, or the intended SameSite tier overridden.

Patches

Patched in undici v6.28.0, v7.29.0, and v8.9.0.

Workarounds

Sanitize domain values against the RFC 1034 letter-digit-hyphen set before passing to setCookie.
Do not pass user-controlled data to the unparsed field.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality low, integrity low, availability none.

Affected software

CVE-2026-16729 is recorded against 1 package.

undici

Timeline and source

Published on 3 August 2026 and last revised on 5 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Web)
github.com (Web)
github.com (Web)
cna.openjsf.org (Web)
github.com (Package)
github.com (Web)
github.com (Web)
github.com (Web)

Details

Severity MEDIUM

CVSS Score 4.8

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

CWE CWE-74

Public Exploit ✅ No

Source OSV

Published 2026-08-03

Updated 2026-08-12

Modified 2026-08-05

Fix URL N/A

Affected Packages

Software	From version	Fixed in
undici	—	—

References

WEB https://github.com/nodejs/undici/security/advisories/GHSA-v3r7-h72x-cjcm

ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-16729

WEB https://github.com/nodejs/undici/commit/10d93fc332f2c8c161982dec3833201de29891b5

WEB https://github.com/nodejs/undici/commit/3bf91ddb493e853957f3a58e155326a668ab8aef

WEB https://github.com/nodejs/undici/commit/af7484043ee075a6f216da0ad77e1dac55199235

WEB https://cna.openjsf.org/security-advisories.html

PACKAGE https://github.com/nodejs/undici

WEB https://github.com/nodejs/undici/releases/tag/v6.28.0

WEB https://github.com/nodejs/undici/releases/tag/v7.29.0

WEB https://github.com/nodejs/undici/releases/tag/v8.9.0

🔗 NVD 🔗 Mitre

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