CVE-2026-13221
Undergoing Analysis
Undergoing Analysis - In Progress
Regular Expression ReDoS in Perl via Trie Overflow
Vulnerability report for CVE-2026-13221, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-07-13
Last updated on: 2026-07-13
Assigner: CPANSec
Description
Description
Perl versions through 5.43.9 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 Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| perl | perl | to 5.43.9 (exc) |
| perl | perl | 5.43.9 |
| perl | perl | 5.38.2 |
| perl | perl | 5.40.2 |
| perl | perl | 5.42.rc1 |
| perl | perl | 5.36.0 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-190 | The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number. |
