CVE-2026-40395
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.
Affected products
12cpe:2.3:a:varnish-software:varnish_enterprise:*:*:*:*:*:*:*:*+ 11 more
- cpe:2.3:a:varnish-software:varnish_enterprise:*:*:*:*:*:*:*:*range: <=6.0.15
- 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:r11:*:*:*:*:*:*
- 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:*:*:*:*:*:*
Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
1- docs.varnish-software.com/security/VEV00003/nvdVendor Advisory
News mentions
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