CVE-2026-4926

HIGH 7.5

path-to-regexp vulnerable to Denial of Service via sequential optional groups

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-400 CWE-1333
Vendor	path-to-regexp
Product	path-to-regexp
Published	Mar 26, 2026
Last Updated	Jul 21, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

Attack Complexity

Privileges Required

User Interaction

Scope

Confidentiality

Integrity

Availability

Affected Versions

path-to-regexp / path-to-regexp

8.0.0 < 8.4.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

Credits

🔍 uug4na blakeembrey UlisesGascon