undici vulnerable to Set-Cookie SameSite attribute downgrade via permissive substring matching

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SUSE CVE-2026-11525

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,...

CVE-2026-11525 undici vulnerable to Set-Cookie SameSite attribute downgrade via permissive substring matching

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,...

CVE-2026-11525

The issue affects undici’s cookie parsing in Set-Cookie headers. The root cause is a permissive substring match for the SameSite attribute during parsing, accepting any value containing Strict, Lax, or None instead of enforcing a case-insensitive exact match per RFC 6265. This can cause downstrea...