CVE-2026-40395 (GCVE-0-2026-40395)
Vulnerability from cvelistv5
Published
2026-04-12 19:21
Modified
2026-04-13 15:45
CWE
  • CWE-770 - Allocation of Resources Without Limits or Throttling
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 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.
Impacted products
Vendor Product Version
varnish-software Varnish Enterprise Version: 6.0.9r5   < 6.0.16r12
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Show details on NVD website


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  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
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