CVE-2026-40394

medium Red Hat
CVSS v3 Base Score
5.9
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score
0.1%
Exploitation probability in 30 days
Top 81% most likely to be exploited
Attack Characteristics
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
None
Availability
High
Published: April 12, 2026 (88 days ago)
Last Modified: April 12, 2026
Vendor: Red Hat
Source: REDHAT

Description

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 transport, and upon upgrading to h2 the HTTP/1 request is repurposed as stream zero. During the upgrade, a buffer allocation is made to reserve space to send frames to the client. This allocation would split the original workspace, and depending on the amount of prefetched data, the next fetch could perform a pipelining operation that would run out of workspace.

CWE

CWE-131

Affected Products

Red Hat Enterprise Linux 10Red Hat Enterprise Linux 8Red Hat Enterprise Linux 9

References

🔗 bugzilla.redhat.com 🔗 www.cve.org 🔗 nvd.nist.gov 🔗 docs.varnish-software.com