{"id":"DEBIAN-CVE-2026-11525","details":"Impact: When undici parses a Set-Cookie header, it accepts any SameSite attribute value that contains Strict, Lax, or None as a substring, rather than the case-insensitive exact match specified by RFC 6265. Non-spec values are silently mapped to one of the three standard tokens. For example, SameSite=NoneOfYourBusiness is parsed as None (the most permissive setting), and SameSite=StrictLax is parsed as Lax (a downgrade from Strict).  Affected applications are those that consume Set-Cookie headers from server responses (for example via undici's fetch or proxy code paths) and then forward or rely on the parsed sameSite attribute. A malicious or non-compliant server can coerce the consumer's view of a cookie's SameSite policy to a weaker value, silently degrading the SameSite enforcement the cookie is supposed to provide.  This was introduced in undici 5.15.0 when the cookies feature was added.  Patches: Upgrade to undici v6.26.0, v7.28.0 or v8.5.0.  Workarounds: After parsing a Set-Cookie header, validate that the resulting sameSite attribute is one of 'Strict', 'Lax', or 'None' (exact, case-insensitive) before forwarding or relying on it.","modified":"2026-08-27T23:05:42.203130870Z","published":"2026-06-17T18:17:35.097Z","upstream":["CVE-2026-11525"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-11525"}],"affected":[{"package":{"name":"node-undici","ecosystem":"Debian:12","purl":"pkg:deb/debian/node-undici?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.15.0+dfsg1+~cs20.10.9.3-1","5.15.0+dfsg1+~cs20.10.9.3-1+deb12u1","5.15.0+dfsg1+~cs20.10.9.3-1+deb12u2","5.15.0+dfsg1+~cs20.10.9.3-1+deb12u3","5.15.0+dfsg1+~cs20.10.9.3-1+deb12u4","5.19.1+dfsg1+~cs20.10.9.5-1","5.19.1+dfsg1+~cs20.10.9.5-2","5.22.1+dfsg1+~cs20.10.10.2-1","5.26.3+dfsg1+~cs23.10.12-1","5.26.3+dfsg1+~cs23.10.12-2","5.26.3+dfsg1+~cs23.10.12-3","5.28.0+dfsg1+~cs23.11.12.3-1","5.28.0+dfsg1+~cs23.11.12.3-2","5.28.2+dfsg1+~cs23.11.12.3-1","5.28.2+dfsg1+~cs23.11.12.3-2","5.28.2+dfsg1+~cs23.11.12.3-3","5.28.2+dfsg1+~cs23.11.12.3-4","5.28.2+dfsg1+~cs23.11.12.3-5","5.28.2+dfsg1+~cs23.11.12.3-6","5.28.4+dfsg1+~cs23.12.11-1","5.28.4+dfsg1+~cs23.12.11-2","7.1.0+dfsg1+~cs24.12.10-1","7.15.0+dfsg+~cs3.2.0-1","7.15.0+dfsg+~cs3.2.0-3","7.16.0+dfsg+~cs3.2.0-1","7.16.0+dfsg+~cs3.2.0-2","7.18.2+dfsg+~cs3.2.0-1","7.2.3+dfsg1+~cs24.12.11-1","7.2.3+dfsg1+~cs24.12.11-2","7.24.5+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-2","7.24.6+dfsg+~cs3.2.0-3","7.3.0+dfsg1+~cs24.12.11-1","7.3.0+dfsg1+~cs24.12.11-2","8.5.0+dfsg+~cs3.2.0-1","8.5.0+dfsg+~cs3.2.0-2","8.5.0+dfsg+~cs3.2.0-3","8.9.0+dfsg+~cs3.2.0-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-11525.json"}},{"package":{"name":"node-undici","ecosystem":"Debian:13","purl":"pkg:deb/debian/node-undici?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["7.15.0+dfsg+~cs3.2.0-1","7.15.0+dfsg+~cs3.2.0-3","7.16.0+dfsg+~cs3.2.0-1","7.16.0+dfsg+~cs3.2.0-2","7.18.2+dfsg+~cs3.2.0-1","7.24.5+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-2","7.24.6+dfsg+~cs3.2.0-3","7.3.0+dfsg1+~cs24.12.11-1","7.3.0+dfsg1+~cs24.12.11-2","8.5.0+dfsg+~cs3.2.0-1","8.5.0+dfsg+~cs3.2.0-2","8.5.0+dfsg+~cs3.2.0-3","8.9.0+dfsg+~cs3.2.0-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-11525.json"}},{"package":{"name":"node-undici","ecosystem":"Debian:14","purl":"pkg:deb/debian/node-undici?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"8.5.0+dfsg+~cs3.2.0-1"}]}],"versions":["7.15.0+dfsg+~cs3.2.0-1","7.15.0+dfsg+~cs3.2.0-3","7.16.0+dfsg+~cs3.2.0-1","7.16.0+dfsg+~cs3.2.0-2","7.18.2+dfsg+~cs3.2.0-1","7.24.5+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-2","7.24.6+dfsg+~cs3.2.0-3","7.3.0+dfsg1+~cs24.12.11-1","7.3.0+dfsg1+~cs24.12.11-2"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-11525.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}