CVE-2026-9679 (GCVE-0-2026-9679)

Vulnerability from cvelistv5 – Published: 2026-06-17 16:56 – Updated: 2026-06-23 16:12
VLAI
Title
undici vulnerable to HTTP header injection via Set-Cookie percent-decoding
Summary
Impact: undici's cookie parser in parseSetCookie percent-decodes cookie values via qsUnescape, turning encoded sequences like %0D%0A, %00, %3B, and %3D into their literal byte equivalents. RFC 6265 §5.4 does not specify any decoding and browsers do not decode either. Applications that parse a Set-Cookie header and then forward the parsed value into a response header (proxies, middleware, SSR frameworks) become vulnerable to HTTP response header injection: an attacker-controlled upstream can inject arbitrary Set-Cookie, Location, or Cache-Control headers into the application's downstream response, enabling session fixation, open redirect, or cache poisoning. Affected applications are those that use undici's cookie parsing (parseSetCookie, parseCookie, getSetCookies) and forward the parsed cookie value into a response header. This was introduced in undici 7.0.0 via PR #3789. Patches: Upgrade to undici v6.26.0, v7.28.0 or v8.5.0. Workarounds: If upgrade is not immediately possible, do not forward values returned by parseSetCookie/parseCookie/getSetCookies directly into response headers; sanitize the value first to strip or reject CR, LF, NUL, ;, and = bytes.
Severity
5.9 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-17 18:31 UTC
CWE
  • CWE-93 - Improper Neutralization of CRLF Sequences ('CRLF Injection')
Assigner
openjs CNA under the redhat root
CNA scorecard C 65/100 over 121 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
undici undici Affected: 0 , < 6.26.0 (semver)
Unaffected: 6.26.0 (semver)
Affected: 7.0.0 , < 7.28.0 (semver)
Unaffected: 7.28.0 (semver)
Affected: 8.0.0 , < 8.5.0 (semver)
Unaffected: 8.5.0 (semver)
guessed Create a notification for this product.
Credits
tndud042713 mcollina KhafraDev UlisesGascon
Show details on NVD website
To clipboard 

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