CVE-2026-19487: CWE-670 Always-Incorrect Control Flow Implementation
CVE-2026-19487 is a vulnerability in Perl versions from 5.9.4 up to but not including 5.41.9 where incorrect regular expression match results occur due to a stale failure flag in the Aho-Corasick prescan. This flaw causes the prescan to end early, potentially missing valid matches or matching on incorrect branches. This can lead to incorrect access or filtering decisions based on the faulty match results.
AI Analysis
Technical Summary
This vulnerability arises from an always-incorrect control flow implementation (CWE-670) in Perl's regular expression engine. Specifically, the Aho-Corasick prescan in S_find_byclass uses a failure flag to track failing transitions, but once set, the flag is not cleared by later successful transitions. As a result, the prescan may stop prematurely, missing earlier candidate matches. For example, the pattern alternation 'ABCF|BCDE|C' on the string 'ABCDE' incorrectly matches 'C' at offset 2 instead of 'BCDE'. This flaw affects Perl versions starting at 5.9.4 through versions before 5.41.9.
Potential Impact
The vulnerability causes Perl's regex engine to produce incorrect match results, which can lead to wrong access control or filtering decisions in applications relying on these matches. This may result in unintended behavior or security policy bypasses where regex matching is critical.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary workaround is provided in the available data. Users should monitor vendor communications for patches addressing this issue.
CVE-2026-19487: CWE-670 Always-Incorrect Control Flow Implementation
Description
CVE-2026-19487 is a vulnerability in Perl versions from 5.9.4 up to but not including 5.41.9 where incorrect regular expression match results occur due to a stale failure flag in the Aho-Corasick prescan. This flaw causes the prescan to end early, potentially missing valid matches or matching on incorrect branches. This can lead to incorrect access or filtering decisions based on the faulty match results.
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability arises from an always-incorrect control flow implementation (CWE-670) in Perl's regular expression engine. Specifically, the Aho-Corasick prescan in S_find_byclass uses a failure flag to track failing transitions, but once set, the flag is not cleared by later successful transitions. As a result, the prescan may stop prematurely, missing earlier candidate matches. For example, the pattern alternation 'ABCF|BCDE|C' on the string 'ABCDE' incorrectly matches 'C' at offset 2 instead of 'BCDE'. This flaw affects Perl versions starting at 5.9.4 through versions before 5.41.9.
Potential Impact
The vulnerability causes Perl's regex engine to produce incorrect match results, which can lead to wrong access control or filtering decisions in applications relying on these matches. This may result in unintended behavior or security policy bypasses where regex matching is critical.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary workaround is provided in the available data. Users should monitor vendor communications for patches addressing this issue.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- CPANSec
- Date Reserved
- 2026-08-10T16:35:50.763Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a7de96abf8831d5396b0490
Added to database: 08/13/2026, 15:57:30 UTC
Last enriched: 08/13/2026, 16:14:59 UTC
Last updated: 08/13/2026, 16:23:55 UTC
Views: 4
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