CVE-2026-40395
Quick assessment
Affected
varnish-software Varnish Enterprise
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
Varnish Enterprise是Varnish公司的一款高性能的缓存软件。用于处理高流量、优化业务。 Varnish Enterprise 6.0.16r12之前版本存在安全漏洞，该漏洞源于共享VCL中headerplus.write_req0函数更新底层req0时，如果修改后的req包含过多标头字段，可能导致工作空间溢出拒绝服务。
Possible ATT&CK Techniques 1 AI
T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2026-40395
Vulnerability Information
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Vulnerability Title
N/A
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5
Vulnerability Title
Varnish Enterprise 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Varnish Enterprise是Varnish公司的一款高性能的缓存软件。用于处理高流量、优化业务。 Varnish Enterprise 6.0.16r12之前版本存在安全漏洞，该漏洞源于共享VCL中headerplus.write_req0函数更新底层req0时，如果修改后的req包含过多标头字段，可能导致工作空间溢出拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| varnish-software | Varnish Enterprise | 6.0.9r5 ~ 6.0.16r12 | - |
|
II. Public POCs for CVE-2026-40395
| # | POC Description | Source Link | Shenlong Link |
|---|
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Same Patch Batch · varnish-software · 2026-04-12 · 3 CVEs total
| CVE-2026-40396 | 4.0 MEDIUM | Varnish Cache 安全漏洞 |
| CVE-2026-40394 | 4.0 MEDIUM | Varnish Cache和Varnish Enterprise 安全漏洞 |
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Same product: Varnish Enterprise
Same weakness: CWE-770
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V. Comments for CVE-2026-40395
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