CVE-2021-36740: Medium severity varnish cache vulnerability

Published Jul 13, 2021
·
Updated

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.

Affected Software

12 affected componentsFixes available
debian/varnish
6.1.1-1+deb10u36.1.1-1+deb10u46.5.1-1+deb11u37.1.1-1.1
Varnish-cache Varnish Cache>=6.0.0<6.0.8
Varnish-cache Varnish Cache=6.0.8-r1
Varnish-cache Varnish Cache=6.0.8-r2
Varnish-software Varnish Cache>=6.0.0<=6.0.5
Varnish-software Varnish Cache>=6.0.0<=6.0.7
Varnish Cache Project Varnish Cache>=5.0.0<=5.2.1
Varnish Cache Project Varnish Cache>=6.1.0<=6.6.0
Fedoraproject Fedora=33
Fedoraproject Fedora=34
Debian Debian Linux=10.0
Debian Debian Linux=11.0

Event History

Jul 13, 2021
Data Sourced
12:00 PM
SeverityAffected Software
Jul 14, 2021
CVE Published
via MITRE·04:07 PM
Data Sourced
via MITRE·04:07 PM
Description
Free Weekly Intel

Don't miss critical vulnerabilities

Join thousands of security professionals who receive our weekly digest of trending CVEs, zero-days, and exploited vulnerabilities.

No spam. Unsubscribe anytime.

Frequently Asked Questions

1

What is the vulnerability ID for this vulnerability?

The vulnerability ID is CVE-2021-36740.

2

What is the severity of CVE-2021-36740?

The severity of CVE-2021-36740 is medium (6.5).

3

Which software versions are affected by CVE-2021-36740?

Varnish Enterprise 6.0.x before 6.0.8r3, 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 are affected by CVE-2021-36740.

4

How can I fix CVE-2021-36740?

To fix CVE-2021-36740, you should update Varnish Cache to version 6.5.2, 6.6.1, or 6.0.8, depending on the software version you are using.

5

Where can I find more information about CVE-2021-36740?

You can find more information about CVE-2021-36740 on the Varnish Software website and the GitHub page of Varnish Cache.

Contact

SecAlerts Pty Ltd.
132 Wickham Terrace
Fortitude Valley,
QLD 4006, Australia
info@secalerts.co
By using SecAlerts services, you agree to our services end-user license agreement. This website is safeguarded by reCAPTCHA and governed by the Google Privacy Policy and Terms of Service. All names, logos, and brands of products are owned by their respective owners, and any usage of these names, logos, and brands for identification purposes only does not imply endorsement. If you possess any content that requires removal, please get in touch with us.
© 2026 SecAlerts Pty Ltd.
ABN: 70 645 966 203, ACN: 645 966 203