CVE-2026-40395

Published: Apr 12, 2026 Last Modified: Apr 13, 2026
ExploitDB:
Other exploit source:
Google Dorks:
MEDIUM 4,0
Source: [email protected]
Attack Vector: network
Attack Complexity: high
Privileges Required: none
User Interaction: none
Scope: changed
Confidentiality: none
Integrity: none
Availability: low

Description

AI Translation Available

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.

EPSS (Exploit Prediction Scoring System)

Trend Analysis

EPSS (Exploit Prediction Scoring System)

Prevede la probabilità di sfruttamento basata su intelligence sulle minacce e sulle caratteristiche della vulnerabilità.

EPSS Score
0,0004
Percentile
0,1th
Updated

EPSS Score Trend (Last 4 Days)

770

Allocation of Resources Without Limits or Throttling

Incomplete
Abstraction: Base Structure: Simple
Common Consequences
Security Scopes Affected:
Availability
Potential Impacts:
Dos: Resource Consumption (Cpu) Dos: Resource Consumption (Memory) Dos: Resource Consumption (Other)
Applicable Platforms
All platforms may be affected
Likelihood of Exploit: High
View CWE Details
https://docs.varnish-software.com/security/VEV00003/
https://docs.varnish-software.com/security/VEV00003/