CVE-2026-4926
path-to-regexp vulnerable to Denial of Service via sequential optional groups
7.5
HIGH
CVSS 3.1
EPSS 0.02%
Description
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.
How to fix CVE-2026-4926
To remediate CVE-2026-4926, upgrade the affected package to a fixed version below.
- —no fix listed
- —upgrade to 8.4.0 or later
Is CVE-2026-4926 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0
- >= 8.0.0, < 8.4.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |