CVE-2026-40394
Publication date 13 April 2026
Last updated 13 April 2026
Ubuntu priority
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.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| varnish | 25.10 questing |
Needs evaluation
|
| 24.04 LTS noble |
Needs evaluation
|
|
| 22.04 LTS jammy |
Needs evaluation
|
|
| 20.04 LTS focal |
Needs evaluation
|
|
| 18.04 LTS bionic |
Needs evaluation
|
|
| 16.04 LTS xenial |
Needs evaluation
|
|
| 14.04 LTS trusty |
Needs evaluation
|
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score |
4.0 · Medium
|
| Attack vector | Network |
| Attack complexity | High |
| Privileges required | None |
| User interaction | None |
| Scope | Changed |
| Confidentiality | None |
| Integrity impact | None |
| Availability impact | Low |
| Vector | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L |