CVE-2026-40394 (GCVE-0-2026-40394)

Vulnerability from cvelistv5 – Published: 2026-04-12 19:17 – Updated: 2026-04-13 15:45
VLAI?
Summary
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.
Severity ?
4 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L
CWE
  • CWE-670 - Always-Incorrect Control Flow Implementation
Assigner
References
Impacted products
Vendor Product Version
varnish-software Varnish Cache Affected: 9.0.0 , < 9.0.1 (semver)
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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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Detection rules are retrieved from Rulezet.