CVE-2026-75628

01/Description

Punk::OAuth2 versions before 0.03 for Perl allow an attacker-chosen off-site redirect after login because same_origin_path accepts a backslash or tab in the return parameter. oauth2_login reads the return parameter from the initiation request, runs same_origin_path over it, and stores the survivor in the session flow record as the post-login redirect target. That check rejects a value that does not begin with a slash, one with a slash as its second byte, and one containing CR or LF. A backslash and a tab pass. The URL Standard treats a backslash as equivalent to a slash for special schemes, so `/\evil.example` parses with the authority `evil.example`. It also strips ASCII tab before parsing, so a tab between two leading slashes leaves `//evil.example`. A crafted link to the application's own login route lands the victim on the attacker's site after a genuine authentication. The redirect carries no authorization code or access token.

02/References6

• datatracker.ietf.org/doc/html/rfc9700#section-4.11.1
• metacpan.org/release/LNATION/Punk-OAuth2-0.02/source/include/po…
• metacpan.org/release/LNATION/Punk-OAuth2-0.03/changes
• url.spec.whatwg.org/#concept-basic-url-parser
• url.spec.whatwg.org/#relative-slash-state
• www.openwall.com/lists/oss-security/2026/08/20/1