Vulnerability in @Koa/router

CVE-2026-9495

Versions of the package @koa/router from 14.0.0 and before 15.0.0 are vulnerable to Access Control Bypass due to the middleware being silently dropped from the execution chain when the router prefix contains path parameters. Depending on what the skipped middleware was supposed to protect, an attacker could bypass authentication and authorization, evade rate limiting or bypass input sanitization.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.3 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L.

EPSS exploit prediction

EPSS: 0.006 (47.5th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 48th percentile — 47.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-9495: held from 0.004 to 0.006.

EPSS over last 30 days · oldest: 0.004 · newest: 0.006 · change: +0.003

Affected products

  • @Koa/router — versions 14.0.0

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-9495?
CVE-2026-9495 is a high-severity vulnerability in @Koa/router, classified under Improper Access Control. CVSS score: 7.3/10. Published 2026-05-26.
How severe is CVE-2026-9495?
High severity. CVSS v3 base score is 7.3 out of 10.