======================================================================== CVE-2026-19953 CPAN Security Group ========================================================================
CVE ID: CVE-2026-19953 Distribution: URI Versions: before 5.36 MetaCPAN: https://metacpan.org/dist/URI VCS Repo: https://github.com/libwww-perl/URI URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep Description ----------- URI versions before 5.36 for Perl encode non-NFC host names to non-standard punycode labels via missing normalization in nameprep. nameprep lowercases each host label but performs no Unicode normalization. IDNA requires a label to be normalized to Form C before it is encoded (RFC 5891), so a label that is not already in NFC is encoded to a different A-label than its normalized form. A label built from the precomposed Devanagari sequence U+0958 U+093E encodes to xn--72b5c without normalization but to xn--11b2fg after NFC normalization, and xn--72b5c does not round-trip back to the original label. Any caller that reads host() from a URI built from untrusted input and uses it for a security decision (an allow or deny list, an SSRF filter, deduplication, a cache key) sees the non-standard label, while a client that fetches the same URL resolves the NFC form, so the check and the fetch can disagree about the host. Problem types ------------- - CWE-1289 Improper Validation of Unsafe Equivalence in Input Solutions --------- Upgrade to URI 5.36 or later. References ---------- https://github.com/libwww-perl/URI/commit/956619a9e94f86d8d2c529b4e06a3674c54a73e7.patch https://github.com/libwww-perl/URI/pull/191 https://metacpan.org/release/OALDERS/URI-5.36/changes https://www.rfc-editor.org/rfc/rfc5891#section-5.2 Credits ------- Naseeb Dangi (naseeb0), Nankai University, finder
