VULNERABILITY INTELLIGENCE

CVE-2026-40394

CVSS score4 MEDIUM
EPSS probability0.24%
CISA KEVNot currently listed
Published2026-04-12
Last modified2026-10-26
CVSS vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L

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.

Weakness classification

  • cve@mitre.org: CWE-670

Primary references