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HIGH · 7.5

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 numbe...

Vulnerability 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.

CVSS Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH

Affected Products

VendorProductVersions
PillarjsPath-To-Regexp>= 8.0.0, < 8.4.0

Related Weaknesses (CWE)

CWE-400CWE-1333

References

FAQ

What is CVE-2026-4926?

CVE-2026-4926 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 numbe...

How severe is CVE-2026-4926?

CVE-2026-4926 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-4926?

Check the references section above for vendor advisories and patch information. Affected products include: Pillarjs Path-To-Regexp.