CVE-2021-36740

varnish: HTTP/2 request smuggling attack via a large Content-Length header for a POST request

Severity Score

6.5

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

*SSVC

Descriptions

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.

Varnish Cache, con HTTP/2 habilitado, permite el contrabando de peticiones y la omisión de autorización de VCL por medio de un encabezado Content-Length grande para una petición POST. Esto afecta a Varnish Enterprise versiones 6.0.x anteriores a 6.0.8r3, y Varnish Cache versiones 5.xy 6.x anteriores a 6.5.2, versiones 6.6.x anteriores a 6.6.1 y versiones 6.0 LTS anteriores a 6.0.8

A flaw was found in Varnish. The Varnish Cache, with HTTP/2 enabled, allows request smuggling and VCL authorization bypass via a large Content-Length header for a POST request. As a result, this flaw allows the information on the Varnish cache to be poisoned. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.

*Credits: N/A

CVSS Scores

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Attack Vector

Network

Attack Complexity

Low

Authentication

None

Confidentiality

Partial

Integrity

Partial

Availability

None

* Common Vulnerability Scoring System

SSVC

Decision:-

Exploitation

Automatable

Tech. Impact

* Organization's Worst-case Scenario

Timeline

2021-07-14 CVE Reserved
2021-07-14 CVE Published
2024-05-22 EPSS Updated
2024-08-04 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

CAPEC

References (9)

URL	Tag	Source

URL	Date	SRC

URL	Date	SRC
https://github.com/varnishcache/varnish-cache/commit/82b0a629f60136e76112c6f2c6372cce77b683be	2023-11-07
https://github.com/varnishcache/varnish-cache/commit/9be22198e258d0e7a5c41f4291792214a29405cf	2023-11-07

URL	Date	SRC
https://docs.varnish-software.com/security/VSV00007	2023-11-07
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/THV2DQA2GS65HUCKK4KSD2XLN3AAQ2V5	2023-11-07
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZHBNLDEOTGYRIEQZBWV7F6VPYS4O2AAK	2023-11-07
https://varnish-cache.org/security/VSV00007.html	2023-11-07
https://www.debian.org/security/2022/dsa-5088	2023-11-07
https://access.redhat.com/security/cve/CVE-2021-36740	2021-08-03
https://bugzilla.redhat.com/show_bug.cgi?id=1982409	2021-08-03

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Varnish-cache Search vendor "Varnish-cache"		Varnish Cache Search vendor "Varnish-cache" for product "Varnish Cache"				>= 6.0.0 < 6.0.8 Search vendor "Varnish-cache" for product "Varnish Cache" and version " >= 6.0.0 < 6.0.8"		plus		Affected
Varnish-cache Search vendor "Varnish-cache"		Varnish Cache Search vendor "Varnish-cache" for product "Varnish Cache"				6.0.8 Search vendor "Varnish-cache" for product "Varnish Cache" and version "6.0.8"		r1, plus		Affected
Varnish-cache Search vendor "Varnish-cache"		Varnish Cache Search vendor "Varnish-cache" for product "Varnish Cache"				6.0.8 Search vendor "Varnish-cache" for product "Varnish Cache" and version "6.0.8"		r2, plus		Affected
Varnish-software Search vendor "Varnish-software"		Varnish Cache Search vendor "Varnish-software" for product "Varnish Cache"				>= 6.0.0 <= 6.0.5 Search vendor "Varnish-software" for product "Varnish Cache" and version " >= 6.0.0 <= 6.0.5"		-		Affected
Varnish-software Search vendor "Varnish-software"		Varnish Cache Search vendor "Varnish-software" for product "Varnish Cache"				>= 6.0.0 <= 6.0.7 Search vendor "Varnish-software" for product "Varnish Cache" and version " >= 6.0.0 <= 6.0.7"		lts		Affected
Varnish Cache Project Search vendor "Varnish Cache Project"		Varnish Cache Search vendor "Varnish Cache Project" for product "Varnish Cache"				>= 5.0.0 <= 5.2.1 Search vendor "Varnish Cache Project" for product "Varnish Cache" and version " >= 5.0.0 <= 5.2.1"		-		Affected
Varnish Cache Project Search vendor "Varnish Cache Project"		Varnish Cache Search vendor "Varnish Cache Project" for product "Varnish Cache"				>= 6.1.0 <= 6.6.0 Search vendor "Varnish Cache Project" for product "Varnish Cache" and version " >= 6.1.0 <= 6.6.0"		-		Affected
Fedoraproject Search vendor "Fedoraproject"		Fedora Search vendor "Fedoraproject" for product "Fedora"				33 Search vendor "Fedoraproject" for product "Fedora" and version "33"		-		Affected
Fedoraproject Search vendor "Fedoraproject"		Fedora Search vendor "Fedoraproject" for product "Fedora"				34 Search vendor "Fedoraproject" for product "Fedora" and version "34"		-		Affected
Debian Search vendor "Debian"		Debian Linux Search vendor "Debian" for product "Debian Linux"				10.0 Search vendor "Debian" for product "Debian Linux" and version "10.0"		-		Affected
Debian Search vendor "Debian"		Debian Linux Search vendor "Debian" for product "Debian Linux"				11.0 Search vendor "Debian" for product "Debian Linux" and version "11.0"		-		Affected