Description (CNA)
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.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Not supplied / Not supplied | affected 0 before 5.36 |
CWE
CWE-1289
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
ADP enrichment
No English description supplied.
No English description supplied.
No references supplied.