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.
References
| Link | Resource |
|---|---|
| https://docs.varnish-software.com/security/VEV00003/ | Vendor Advisory |
Configurations
Configuration 1 (hide)
|
History
17 Apr 2026, 14:37
| Type | Values Removed | Values Added |
|---|---|---|
| References | () https://docs.varnish-software.com/security/VEV00003/ - Vendor Advisory | |
| First Time |
Varnish-software varnish Enterprise
Varnish-software |
|
| CPE | cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r5:*:*:*:*:*:* cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r2:*:*:*:*:*:* cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r6:*:*:*:*:*:* cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r10:*:*:*:*:*:* cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r8:*:*:*:*:*:* cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r9:*:*:*:*:*:* cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r11:*:*:*:*:*:* cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r4:*:*:*:*:*:* cpe:2.3:a:varnish-software:varnish_enterprise:*:*:*:*:*:*:*:* cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r3:*:*:*:*:*:* cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r7:*:*:*:*:*:* cpe:2.3:a:varnish-software:varnish_enterprise:6.0.16:r1:*:*:*:*:*:* |
12 Apr 2026, 20:16
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-04-12 20:16
Updated : 2026-04-17 14:37
NVD link : CVE-2026-40395
Mitre link : CVE-2026-40395
CVE.ORG link : CVE-2026-40395
JSON object : View
Products Affected
varnish-software
- varnish_enterprise
CWE
CWE-770
Allocation of Resources Without Limits or Throttling