CVE-2026-40396
varnish: Varnish Cache: Denial of Service via workspace overflow during HTTP/1 pipelining
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. A malicious client can exploit a 'workspace overflow' vulnerability by sending an HTTP/1 request, waiting for the session to release its worker thread, and then resuming traffic with multiple requests to trigger a pipelining operation. This can lead to a workspace overflow, causing the Varnish server to panic and crash, resulting in a Denial of Service (DoS).
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