CVE-2026-19487
Perl versions from 5.9.4 before 5.41.9 produce incorrect regular expression match results when a stale failure flag ends the Aho-Corasick prescan early in S_find_byclass. The prescan walks the subject for positions where the full pattern could match, and the engine tries it from the leftmost one recorded. A failing transition sets the failed flag, and a later successful transition does not clear it, so the prescan reads the stale flag as a failure and stops before it can record a candidate that starts earlier. It takes a subject where one candidate is recorded and a later character then forces a fallback through a fail link that succeeds. Example: "ABCDE" =~ m/ABCF|BCDE|C/; # matches C at offset 2, not BCDE "ABCDE" =~ m/ABCF|BCDE|C(G)/; # no match, BCDE missed An alternation like this can miss input it should match, or match it on the wrong branch, so an access or filtering decision made from the result can be wrong.
Scoring
- Severity
- MEDIUM
- CVSS base score
- 5.3
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- EPSS probability
- 0.42%
- CWE
- CWE-670
- Published
- 2026-08-13
- Last modified
- 2026-08-13
Weakness type
Related vulnerabilities
- CVE-2026-55624 — MintyItanium Lost-Auction takes items like barrier blocks out from search GUI
- CVE-2026-72705 — Rocq Prover before 9.2.0 Guard Checker Accepts Fixpoint Passed as a Higher-Order Argument
- CVE-2026-72704 — Rocq Prover through 9.2.0 Guard Checker Trusts Corrupted Recursive Tree After Transport
- CVE-2026-72703 — Rocq Prover 8.20 before 9.2.0 Guard Checker Accepts Non-Terminating Fixpoint via Unchecked Cross-Calls
- CVE-2026-73283 — In sshd in OpenSSH before 10.5, the restrict keyword (in authorized_keys) was supposed to be...
- CVE-2026-20713 — Always-incorrect control flow implementation in some firmware for some Intel(R) Xeon(R) processors...
- CVE-2026-14935 — Gstreamer: gstreamer: webrtcbin accepts remote sdp without a=fingerprint due to inverted presence check
- CVE-2026-56328 — Capgo - Integrity Issue in Release Routing via Multiple Public Channels