Dashboard / CVE-2026-13221

CVE-2026-13221

CRITICAL
INFO Priority: 0.04 BB Relevance: 78/100
Published: 2026-07-13 Modified: 2026-10-24 First seen: 2026-10-29 Status: active

Attack Surface

Network Low Complexity No Auth No Interaction Integ. Impact

CVSS Vector Breakdown

AV: Network
AC: Low
PR: None
UI: None
S: Unchanged
C: None
I: High
A: High

Description

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.

Weakness Classification (1)

Affected Software (1)

VendorProductVersion
perl perl < 5.43.9

References & Advisories (3)

http://www.openwall.com/lists/oss-security/2026/07/13/5
Mailing List Patch Third Party Advisory

Bug Bounty Relevance

78 / 100
✓ Network accessible
✓ No authentication
✓ Low complexity
✓ No user interaction

CVSS Score

9.1 / 10.0 v3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

EPSS — Exploitation Probability

0.49%
Raw Score 0.004940
Percentile 42.4%
Date 2026-10-29

EPSS Trend

2026-10-29
0.00494
2026-10-28
0.00494

Intelligence Sources

nvd ref →

External Links