CVE-2026-13221

Perl versions before 5.40.5-RC1, from 5.41.0 before 5.42.3-RC1, from 5.43.0 before 5.43.10 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.

CVSS v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/Perl/perl5/commit/03f74bbbd3a68350d926ee93d56ee4808c28c4c7.patch	Patch
https://github.com/Perl/perl5/issues/23388	Issue Tracking
http://www.openwall.com/lists/oss-security/2026/07/13/5	Mailing List Patch Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:perl:perl:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-07-13 17:16

Updated : 2026-09-08 22:17

NVD link : CVE-2026-13221

Mitre link : CVE-2026-13221

CVE.ORG link : CVE-2026-13221

JSON object : View

Products Affected

perl

perl

CWE

CWE-190

Integer Overflow or Wraparound

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