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.
Published:Mar 26, 2026
Last Modified:Sep 9, 2026
EPS:Mar 26, 2026
EPSS Score:0.00791
CVSS Score:7.5
Affected Products
Vendor
Product
Action
Vendor
Path-to-regexp
Product
Path-to-regexp
Path-to-regexp
Path-to-regexp
Vendor
Pillarjs
Product
Path-to-regexp
Pillarjs
Path-to-regexp
Exploits
No exploit reference
Common Weakness Enumeration
Common Attack Pattern Enumeration and Classification (CAPEC)
Related CVEs
References
Common Vulnerability Scoring System
Attack Vector
Network
Adjacent
Local
Physical
Privileges Required
None
Low
High
User Interaction
None
Required
Scope
Unchanged
Changed
Confidentiality
None
Low
High
Integrity
None
Low
High
Availability
None
Low
High
