CVE catalog

CVE-2021-36740

varnish: CVE-2021-36740

Severity: High · CVSS 8.1CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: Jul 13, 2021, 12:00:00 AM UTC
Source: [NVD] · [CVE record]
EPSS: 1.60% · Oct 25, 2026

Varnish Cache, with HTTP/2 enabled, allows request smuggling and VCL authorization bypass via a large Content-Length header for a POST request. This affects Varnish Enterprise 6.0.x before 6.0.8r3, and Varnish Cache 5.x and 6.x before 6.5.2, 6.6.x before 6.6.1, and 6.0 LTS before 6.0.8.

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`	fixed
Debian	varnish	trixie-security	`7.7.0-3+deb13u2`	fixed
Debian	varnish	bookworm	`7.1.1-2+deb12u1`	fixed
Debian	varnish	bookworm-security	`7.1.1-2+deb12u1`	fixed
Alpine	varnish	3.11	`6.5.2-r0`	fixed
Alpine	varnish	3.12	`6.5.2-r0`	fixed
Alpine	varnish	3.13	`6.5.2-r0`	fixed
Alpine	varnish	3.14	`6.6.1-r0`	fixed
Alpine	varnish	3.15	`6.6.1-r0`	fixed
Alpine	varnish	3.16	`6.6.1-r0`	fixed
Alpine	varnish	3.17	`6.6.1-r0`	fixed
Alpine	varnish	3.18	`6.6.1-r0`	fixed
Alpine	varnish	3.19	`6.6.1-r0`	fixed
Alpine	varnish	3.20	`6.6.1-r0`	fixed
Alpine	varnish	3.21	`6.6.1-r0`	fixed
Alpine	varnish	3.22	`6.6.1-r0`	fixed
Alpine	varnish	3.23	`6.6.1-r0`	fixed
Alpine	varnish	3.24	`6.6.1-r0`	fixed
Ubuntu	varnish	20.04	`6.1.1-1`	vulnerable
Ubuntu	varnish	20.04	`6.2.1-2`	vulnerable
Ubuntu	varnish	20.04	`6.2.1-2ubuntu0.1`	fixed
Suse	varnish	package hub 15 sp3	`7.1.0-bp153.2.3.1`	fixed
Opensuse	varnish	leap 15.3	`7.1.0-bp153.2.3.1`	fixed

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	varnish	source	trixie	`6.5.2-1`	not yet assigned	Not reported	[991040]
Debian	varnish	source	bookworm	`6.5.2-1`	not yet assigned	Not reported	[991040]
Alpine	varnish	apk	3.11	`6.5.2-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.12	`6.5.2-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.13	`6.5.2-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.14	`6.6.1-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.15	`6.6.1-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.16	`6.6.1-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.17	`6.6.1-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.18	`6.6.1-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.19	`6.6.1-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.20	`6.6.1-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.21	`6.6.1-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.22	`6.6.1-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.23	`6.6.1-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Alpine	varnish	apk	3.24	`6.6.1-r0`	Not reported	ALPINE-CVE-2021-36740	Not reported
Ubuntu	varnish	deb	20.04	`6.2.1-2ubuntu0.1`	Not reported	UBUNTU-CVE-2021-36740	Not reported
Suse	varnish	rpm	package hub 15 sp3	`7.1.0-bp153.2.3.1`	Not reported	OPENSUSE-SU-2022:0148-1	Not reported
Opensuse	varnish	rpm	leap 15.3	`7.1.0-bp153.2.3.1`	Not reported	OPENSUSE-SU-2022:0148-1	Not reported

[Debian bug #991040]

OpenFactory catalog packages

Matching against OpenFactory catalog package versions is in progress.

[Debian 12 (Bookworm)]

[libvarnishapi3]Unknown
Source package: [varnish]
Details (4)
- 7.1.1-2+deb12u1 · amd64 · bookworm
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · arm64 · bookworm
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · amd64 · bookworm-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · arm64 · bookworm-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
[libvarnishapi-dev]Unknown
Source package: [varnish]
Details (4)
- 7.1.1-2+deb12u1 · amd64 · bookworm
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · arm64 · bookworm
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · amd64 · bookworm-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · arm64 · bookworm-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
[varnish]Unknown
Details (4)
- 7.1.1-2+deb12u1 · amd64 · bookworm
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · arm64 · bookworm
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · amd64 · bookworm-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · arm64 · bookworm-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
[varnish-doc]Unknown
Source package: [varnish]
Details (4)
- 7.1.1-2+deb12u1 · all · bookworm
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · all · bookworm
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · all · bookworm-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12
- 7.1.1-2+deb12u1 · all · bookworm-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · bookworm; dsa · varnish · debian · 12

[Debian 13 (Trixie)]

[libvarnishapi3]Unknown
Source package: [varnish]
Details (4)
- 7.7.0-3+deb13u1 · amd64 · trixie
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · arm64 · trixie
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · amd64 · trixie-security · Historical version
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · arm64 · trixie-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
[libvarnishapi-dev]Unknown
Source package: [varnish]
Details (4)
- 7.7.0-3+deb13u1 · amd64 · trixie
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · arm64 · trixie
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · amd64 · trixie-security · Historical version
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · arm64 · trixie-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
[varnish]Unknown
Details (4)
- 7.7.0-3+deb13u1 · amd64 · trixie
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · arm64 · trixie
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · amd64 · trixie-security · Historical version
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · arm64 · trixie-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
[varnish-doc]Unknown
Source package: [varnish]
Details (4)
- 7.7.0-3+deb13u1 · all · trixie
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · all · trixie
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · all · trixie-security
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13
- 7.7.0-3+deb13u1 · all · trixie-security · Historical version
  Fixed · Fixed: 6.5.2-1
  dsa · varnish · debian · 13

Observed: Oct 23, 2026, 5:58:56 PM UTC

References

[Debian Security Tracker] · [FIRST EPSS] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]