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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

Quick assessment

Affected
CVE-2026-13221
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

SHAY perl是SHAY的编程语言解释器。 SHAY perl 5.43.9及之前版本存在数字错误漏洞，该漏洞源于在Perl_study_chunk中将超过65535个固定字符串分支编译为trie时，分支计数溢出16位字段导致trie匹配决策表截断，可能产生误报和漏报的正则表达式匹配结果。

AI Predicted 7.4 Difficulty: Moderate EPSS 0.43% · P36

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 3

VendorProduct Version RangeStatus
None None < 5.40.5-RC1 affected
5.41.0< 5.42.3-RC1 affected
5.43.0< 5.43.10 affected

I. Basic Information for CVE-2026-13221

Vulnerability Information
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Vulnerability Title
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
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
整数溢出或超界折返
Source: CVE Program / CVE List V5
Vulnerability Title
SHAY perl 数字错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
SHAY perl是SHAY的编程语言解释器。 SHAY perl 5.43.9及之前版本存在数字错误漏洞，该漏洞源于在Perl_study_chunk中将超过65535个固定字符串分支编译为trie时，分支计数溢出16位字段导致trie匹配决策表截断，可能产生误报和漏报的正则表达式匹配结果。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
- - 0 ~ 5.40.5-RC1 -

II. Public POCs for CVE-2026-13221

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III. Intelligence Information for CVE-2026-13221

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Patches & Fixes for CVE-2026-13221 (2)

IV. Related Vulnerabilities

Same weakness: CWE-190

V. Comments for CVE-2026-13221

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