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

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: 2026-03-26 Last update: 2026-04-16 Assigner: ce714d77-add3-4f53-aff5-83d477b104bb Source: ce714d77-add3-4f53-aff5-83d477b104bb
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-4926 is rated Low Risk (31.8/100): CVSS High severity, with low exploitation likelihood (EPSS 0.02%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-4926

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-22 0.05% 0.02% -0.03%
2 2026-04-01 0.04% 0.05% +0.01%
3 2026-03-27 — 0.04% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-4926

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 ce714d77-add3-4f53-aff5-83d477b104bb

Weakness enumeration for CVE-2026-4926

GitHub Security Advisory for CVE-2026-4926

GHSA-j3q9-mxjg-w52f · Severity: high · Ecosystem: npm — path-to-regexp vulnerable to Denial of Service via sequential optional groups

OS Trackers for CVE-2026-4926

vendor priority summary link
debian not yet assigned CVE-2026-4926 not yet assigned priority: Debian including 1 source packages (node-path-to-regexp), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 3, resolved 2. https://security-tracker.debian.org/tracker/CVE-2026-4926
redhat high — https://access.redhat.com/security/cve/CVE-2026-4926
ubuntu medium CVE-2026-4926 medium priority: Ubuntu including 1 source packages (node-path-to-regexp), 7 status rows across 7 suites (bionic, focal, jammy, noble, questing, upstream, xenial): needs-triage 6, released 1. https://ubuntu.com/security/CVE-2026-4926

Affected software / configurations for CVE-2026-4926

Vendor Product Version Raw CPE
pillarjs path-to-regexp >= 8.0.0, < 8.4.0 cpe:2.3:a:pillarjs:path-to-regexp:*:*:*:*:*:node.js:*:*

References for CVE-2026-4926

URL Tags
https://cna.openjsf.org/security-advisories.html Third Party Advisory
cvelogic Threat Intelligence