CVE-2026-13221

unknown

Published 2026-07-13 · Modified 2026-07-13

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CVSS v3

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CVSS v4 NEW

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not yet in upstream

VIR risk

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Description

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.

Predictions

Exploit likelihood

20%

Patch ETA

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Heuristic predictions, AS-IS, for prioritization only.

Mitigations

Mitigation details

Source: Debian Security Tracker · View original ↗ · DFSG

CVE-2026-13221 NameCVE-2026-13221 DescriptionPerl versions through 5.43.9 produce silently incorrect regular expres ... SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) Vulnerable and fixed packages The table below lists information on source packages. Source…

CVE-2026-13221

Name	CVE-2026-13221
Description	Perl versions through 5.43.9 produce silently incorrect regular expres ...
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
perl (PTS)	bullseye	5.32.1-4+deb11u3	vulnerable
	bullseye (security)	5.32.1-4+deb11u5	vulnerable
	bookworm	5.36.0-7+deb12u3	vulnerable
	bookworm (security)	5.36.0-7+deb12u2	vulnerable
	trixie	5.40.1-6	vulnerable
	forky, sid	5.40.1-8	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
perl	source	(unstable)	(unfixed)

Notes

https://lists.security.metacpan.org/cve-announce/msg/41780104/
https://github.com/Perl/perl5/issues/23388
Introduced with: https://github.com/Perl/perl5/commit/acababb42be12ff2986b73c1bfa963b70bb5d54e (v5.37.10)
Fixed by: https://github.com/Perl/perl5/commit/03f74bbbd3a68350d926ee93d56ee4808c28c4c7 (v5.43.10)

Home - Debian Security - Source (Git)

Apply commands

text fix

Notes

https://lists.security.metacpan.org/cve-announce/msg/41780104/https://github.com/Perl/perl5/issues/23388Introduced with: https://github.com/Perl/perl5/commit/acababb42be12ff2986b73c1bfa963b70bb5d54e (v5.37.10)Fixed by: https://github.com/Perl/perl5/commit/03f74bbbd3a68350d926ee93d56ee4808c28c4c7 (v5.43.10)

OS impact

Debian Affected 5 releases

Version	Status	Fixed in
trixie	Affected	—
sid	Affected	—
forky	Affected	—
bullseye	Affected	—
bookworm	Affected	—

References

CWEs

CWE-190

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.