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CVE-2026-13221 on CTRL-OS 26.05

Aliases: CVE-2026-13221

Packages: perl

Status: Plausible

Advisory Information

Perl versions through 5.43.9 produce silently incorrect regular expression matches when an alternation of more than 65535 fixed string branches is compiled into a trie in Perl_study_chunk.

When such branches are combined into a trie, the delta between the first branch and the shared tail is stored in a 16-bit field. A branch count above 65535 overflows the field, and the trie's match decision table is truncated with no warning or error.

A pattern of this shape produces false positive matches (matching strings it should not) and false negative matches (failing to match strings it should). When such a pattern gates an access or filtering decision, the result is wrong.

Updates

2026-07-14 15:58 CEST

Metadata changes:

  • Status for package perl: “Plausible”

(Amended on: 2026-07-14 20:00 CEST)

2026-07-14 15:57 CEST

Metadata changes:

  • Status for package perl: “New”