CVE-2026-16729: undici vulnerable to cookie attribute injection via unsanitized domain and unparsed setCookie fields

CSIRTS triage

What

Cookie attribute injection vulnerability due to unsanitized domain and unparsed setCookie fields.

Who is affected

Applications using undici HTTP client library.

Urgency

Medium priority with CVSS 4.8; not yet exploited but allows cookie manipulation.

Action

Update undici to a patched version.

AI-assisted analysis generated from the source advisory — verify against the original.

Details

Source

Microsoft Security Response Center (INTL · vendor-psirt · site)

Severity

medium — CVSS 4.8

Published

2026-08-06

Exploitation

Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-16729

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

• Low exploitation riskCVE-2026-167290.17% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 6% of all EPSS-scored CVEs.

Referenced CVEs

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

• mediumGHSA-v3r7-h72x-cjcm: undici vulnerable to cookie attribute injection via unsanitized domain and unparsed setCo…ghsa
• mediumCVE-2026-16729: undici's setCookie function does not fully sanitize cookie attributes. In undici before 6.28.0…nvd

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