CVE-2026-40395_CVE-2026-40395

4 / 10

MEDIUM

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

Description

Varnish Enterprise before 6.0.16r12 allows a "workspace overflow" denial of service (daemon panic) for shared VCL. The headerplus.write_req0() function from vmod_headerplus updates the underlying req0, which is normally the original read-only request from which req is derived (readable and writable from VCL). This is useful in the active VCL, after amending req, to prepare a refined req0 before switching to a different VCL with the return (vcl(<label>)) action. This is for example how the Varnish Controller operates shared VCL deployments. If the amended req contained too many header fields for req0, this would have resulted in a workspace overflow that would in turn trigger a panic and crash the Varnish Enterprise server. This could be used as a Denial of Service attack vector by malicious clients.

Basic Information

ID CVE-2026-40395

Source mitre

Published Apr 12, 2026 at 19:21

Modified Apr 12, 2026 at 19:33

Affected Product

Vendor varnish-software

Product Varnish Enterprise

Version 6.0.9r5

Affected Versions varnish-software Varnish Enterprise 6.0.9r5

CWE Classification

CWE-770

References

docs.varnish-software.com /security/VEV00003/

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