Improper Neutralization of Special Elements in Output Used by a Downstream Component in undici - CVE-2026-16729
Published: July 29, 2026
Vulnerability identifier: #VU140036
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-16729
CWE-ID: CWE-74
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Affected software:
undici
undici
Detailed vulnerability description
The vulnerability allows a remote attacker to bypass cookie security protections and modify cookie attributes.
The vulnerability exists due to improper neutralization of special elements in output used by a downstream component in the setCookie function when processing user-controlled domain or unparsed setCookie fields. A remote attacker can supply crafted input containing cookie attributes to bypass cookie security protections and modify cookie attributes.
Exploitation requires an application to pass user-controlled input to these fields, such as in multi-tenant or reverse-proxy deployments.
How to mitigate CVE-2026-16729
Install security update from vendor's website.