Home/CVE/Impact: A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax
CVE

CVE-2026-4926

Impact: A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax

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.

HIGH · CVSS 7.5 EPSS 0.00019
Schedule remediation
  • SSVC automatable: yes - attacks can be scripted at scale
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-1333Inefficient Regular Expression Complexity
CWE-400Uncontrolled Resource Consumption
▤

Affected Products & Versions

1
pillarjs path-to-regexp>= 8.0.0 and < 8.4.0
▤

Affected Packages

1
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
npm path-to-regexp HIGH fixed in 8.4.0
▣

Scoring & Timeline

7.5
HIGH · CVSS v3.1 · ce714d77-add3-4f53-aff5-83d477b104bb
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD26 Mar 2026 · 07:17 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
yes
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

10
rhsaRHSA-2026:13545Important
rhsaRHSA-2026:17789Important
rhsaRHSA-2026:13826Important
rhsaRHSA-2026:10175Important
rhsaRHSA-2026:10153Important
🔗

References & Sources

1
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://cna.openjsf.org/security-advisories.htmlThird Party Advisory
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