CVE-2026-40394

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Summary

CVECVE-2026-40394
StatePUBLISHED
Assignermitre
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-12 20:16:17 UTC
Updated2026-04-13 15:01:43 UTC
DescriptionVarnish 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.

Risk And Classification

Primary CVSS: v3.1 4 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L

EPSS: 0.000390000 probability, percentile 0.115050000 (date 2026-04-14)

Problem Types: CWE-670 | CWE-670 CWE-670 Always-Incorrect Control Flow Implementation

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L
3.1CNACVSS4MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
Low

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Varnish-software Varnish Cache affected 9.0.0 9.0.1 semver Not specified

References

ReferenceSourceLinkTags
docs.varnish-software.com/security/VEV00002 [email protected] docs.varnish-software.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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