CVE Catalog

CVE-2026-40395

MediumCVSS 4.0
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.24%

15th percentile - higher than 15% of all known CVEs

Summary

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 req0; if the amended req contains too many header fields, it can cause a workspace overflow and crash the server.

Risk Assessment

A malicious client could crash the Varnish Enterprise server, causing service unavailability.

Recommendation

Update Varnish Enterprise to version 6.0.16r12 or later.

Related vulnerabilities

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS