{"schemaVersion":3,"id":"CVE-2026-40395","aliases":["UBUNTU-CVE-2026-40395"],"status":"published","duplicateOf":null,"title":null,"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. 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