Resource exhaustion in path-to-regexp - CVE-2026-4926
Published: November 9, 2026
Vulnerability identifier: #VU162702
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-4926
CWE-ID: CWE-400
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows an unauthenticated remote attacker to cause denial of service in applications that accept user-controlled route patterns.
The vulnerability exists due to exponential growth in regular expressions generated by path-to-regexp when route patterns contain multiple sequential optional groups using curly brace syntax. An unauthenticated remote attacker can submit a route pattern containing many such groups to exhaust resources during regular expression generation.
Affected software
path-to-regexp
How to mitigate CVE-2026-4926
Install security update from vendor's website.
path-to-regexp - update to 8.4.0