CVE-2026-4926
Impact: A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as `{a}{b}{c}:z`. The generated regex grows exponentially with the number of groups, causing denial of service. Patches: Fixed in version 8.4.0. Workarounds: Limit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.
Scoring
- Severity
- HIGH
- CVSS base score
- 7.5
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS probability
- 0.79%
- CWE
- CWE-400, CWE-1333
- Published
- 2026-03-26
- Last modified
- 2026-09-14
Affected products
- path-to-regexp path-to-regexp
- path-to-regexp path-to-regexp
Weakness type
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