GHSA-G8M3-5G58-FQ7M 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: -...

CVE-2026-11525

A flaw was found in undici. When undici processes Set-Cookie headers, it incorrectly interprets the SameSite attribute, accepting partial matches instead of exact ones. This allows a malicious server to downgrade a cookie's SameSite policy to a less secure setting, potentially leading to unintend...