CVE catalog

CVE-2026-40395

Severity: Medium · CVSS 4CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L
Published: Jan 1, 2026, 12:00:00 AM UTC
Source: [NVD] · [CVE record]
EPSS: 0.24% · Oct 25, 2026

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.

Vulnerable and fixed packages

Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.

Distribution	Package	Release	Version	Status
Debian	varnish	trixie	`7.7.0-3+deb13u1`	not affected
Debian	varnish	trixie-security	`7.7.0-3+deb13u2`	not affected
Debian	varnish	bookworm	`7.1.1-2+deb12u1`	not affected
Debian	varnish	bookworm-security	`7.1.1-2+deb12u1`	not affected
Cpe	varnish_enterprise	Not reported	Not reported	unknown
Cpe	varnish_enterprise	Not reported	Not reported	unknown

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	varnish	source	trixie	`Not affected`	unimportant	Not reported	Not reported
Debian	varnish	source	bookworm	`Not affected`	unimportant	Not reported	Not reported

OpenFactory catalog packages

[Debian 12 (Bookworm)]

[libvarnishapi3]Not affected
Source package: [varnish]
Details (4)
- 7.1.1-2+deb12u1 · amd64 · bookworm
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · arm64 · bookworm
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · amd64 · bookworm-security
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · arm64 · bookworm-security
  Not affected
  nvd · varnish · debian · bookworm
[libvarnishapi-dev]Not affected
Source package: [varnish]
Details (4)
- 7.1.1-2+deb12u1 · amd64 · bookworm
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · arm64 · bookworm
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · amd64 · bookworm-security
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · arm64 · bookworm-security
  Not affected
  nvd · varnish · debian · bookworm
[varnish]Not affected
Details (4)
- 7.1.1-2+deb12u1 · amd64 · bookworm
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · arm64 · bookworm
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · amd64 · bookworm-security
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · arm64 · bookworm-security
  Not affected
  nvd · varnish · debian · bookworm
[varnish-doc]Not affected
Source package: [varnish]
Details (4)
- 7.1.1-2+deb12u1 · all · bookworm
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · all · bookworm
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · all · bookworm-security
  Not affected
  nvd · varnish · debian · bookworm
- 7.1.1-2+deb12u1 · all · bookworm-security
  Not affected
  nvd · varnish · debian · bookworm

Observed: Oct 27, 2026, 7:59:11 AM UTC

References

[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [Red Hat security advisories and VEX]