Instituto Nacional de ciberseguridad. Sección Incibe
Instituto Nacional de Ciberseguridad. Sección INCIBE-CERT

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CVE-2026-40394

Severity CVSS v4.0:
Pending analysis
Type:
Unavailable / Other
Publication date:
12/04/2026
Last modified:
17/04/2026

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.

Impact

Vector 3.x
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L CVSS v3.1 Severity and Metrics:

Base Score: 4.00 MEDIUM
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L

Attack Vector (AV): Network
Attack Complexity (AC): High
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Changed
Confidentiality (C): None
Integrity (I): None
Availability (A): Low

Base Score 3.x
4.00
Severity 3.x
MEDIUM

Vulnerable products and versions

CPE From Up to
cpe:2.3:a:varnish-software:varnish_enterprise:*:*:*:*:*:*:*:* 6.0.15 (including)
cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r1:*:*:*:*:*:*
cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r10:*:*:*:*:*:*
cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r2:*:*:*:*:*:*
cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r3:*:*:*:*:*:*
cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r4:*:*:*:*:*:*
cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r5:*:*:*:*:*:*
cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r6:*:*:*:*:*:*
cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r7:*:*:*:*:*:*
cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r8:*:*:*:*:*:*
cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r9:*:*:*:*:*:*
cpe:2.3:a:vinyl-cache:vinyl_cache:9.0.0:*:*:*:*:*:*:*

To consult the complete list of CPE names with products and versions, see this page


References to Advisories, Solutions, and Tools