CVE-2021-36740

high
Published — · Modified —
CVSS v3
CVSS v2
VIR risk
8.0

Description

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.

Predictions

Exploit likelihood
20%
Patch ETA

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2021-36740

vendor Authored 2026-05-27

Vendor advisory: rocky — https://errata.rockylinux.org/RLSA-2021:2988

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2021-36740.html

OS impact

OSVersionStatusFixed in
suse slesaffected
rockylinux rocky8fixed
debian debianbookwormfixed6.5.2-1
debian debianbullseyefixed6.5.1-1+deb11u2
debian debianforkyfixed6.5.2-1
debian debiansidfixed6.5.2-1
debian debiantrixiefixed6.5.2-1

References

Verify integrity in audit chain (admin only). AS-IS.