What is CVE-2026-40394?

CVE-2026-40394 is a medium-severity vulnerability in Varnish-software Varnish Cache, classified under Always-Incorrect Control Flow Implementation. CVSS score: 4.0/10. Published 2026-04-12.

How severe is CVE-2026-40394?

Medium severity. CVSS v3 base score is 4.0 out of 10.

Vulnerability in Varnish-software Varnish Cache

CVE-2026-40394

Varnish Cache 9 before 9.0.1 and Varnish Enterprise before 6.0.16r11 allows a "workspace overflow" denial of service (daemon panic) for certain amounts of prefetched data. The setup of an HTTP/2 session starts with a speculative HTTP/1 tra…

EPSS: 0.001 (19.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.0 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L.

Affected products

Varnish-software Varnish Cache — versions 9.0.0

Weakness classification (CWE)

CWE-670 — Always-Incorrect Control Flow Implementation

References

docs.varnish-software.com/security/VEV00002/

Frequently asked questions

What is CVE-2026-40394?: CVE-2026-40394 is a medium-severity vulnerability in Varnish-software Varnish Cache, classified under Always-Incorrect Control Flow Implementation. CVSS score: 4.0/10. Published 2026-04-12.
How severe is CVE-2026-40394?: Medium severity. CVSS v3 base score is 4.0 out of 10.