PT-2026-32184 · Varnish · Varnish Enterprise+1

CVE-2026-40395 · Published 2026-04-12 · Updated 2026-04-13

Positive Technologies (AI Summary)

CVSS v3.1

7.5

High

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Name of the Vulnerable Software and Affected Versions Varnish Enterprise versions prior to 6.0.16r12

Description Varnish Enterprise versions before 6.0.16r12 are susceptible to a denial of service (daemon panic) due to a workspace overflow when handling shared VCL. The headerplus.write req0() function within the vmod headerplus module updates the req0 object, which is typically a read-only copy of the original request. If the modified request contains an excessive number of header fields, it can cause a workspace overflow, leading to a panic and crash of the Varnish Enterprise server. This can be exploited as a Denial of Service attack vector.

Recommendations Update to version 6.0.16r12 or later.

Fix

DoS

Allocation of Resources Without Limits

Weakness Enumeration

CWE-770

Related Identifiers

CVE-2026-40395

Affected Products

Varnish Enterprise

Vmod Headerplus

References · 7

• https://nvd.nist.gov/vuln/detail/CVE-2026-40395 · Security Note
• https://cve.org/CVERecord?id=CVE-2026-40395 · Security Note
• https://docs.varnish-software.com/security/VEV00003 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-40395 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-40395 · Vendor Advisory
• https://twitter.com/VulmonFeeds/status/2043435191708839947 · Twitter Post
• https://twitter.com/CVEnew/status/2043561041586475492 · Twitter Post