CVE-2026-4926 HIGH

CVE-2026-4926: path-to-regexp vulnerable to Denial of Service via sequential optional groups

Vendor Path-To-Regexp
Product path-to-regexp
Weakness CWE-400
Published March 26, 2026
Last update June 30, 2026
View on NVD All CVEs

CVSS base score

7.5/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality None
Integrity None

CVSS vector

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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

March 26, 2026 CVE published
June 30, 2026 Record updated