CVE-2026-40394
Varnish Cache: Varnish Enterprise: Varnish Cache and Varnish Enterprise: Denial of Service via workspace overflow
Severity
ModerateRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · April 13, 2026
Updated · June 28, 2026
Description
A flaw was found in Varnish Cache and Varnish Enterprise. A remote attacker can trigger a denial of service by sending specific amounts of prefetched data during an HTTP/2 session upgrade. This vulnerability, known as a "workspace overflow," occurs when the system attempts to allocate a buffer, splitting the available memory workspace. Subsequent data processing then exhausts this limited workspace, causing the Varnish daemon to panic and become unavailable.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
No mitigation is specified in collected source.
CVSS / CWE
CVSS 3.1 · 5.9CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE-131 · Incorrect Calculation of Buffer Size