Vulnerability in Varnish-Cache Varnish Cache
CVE-2021-36740
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.
Vulnerability class: HTTP Request Smuggling
EPSS: 0.016 (74.7th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.
Affected products
- Varnish-cache Varnish_cache — versions 6.0.8
- Varnish_cache_project Varnish_cache
- Varnish-software Varnish_cache
- Debian Debian_linux — versions 10.0, 11.0
- Fedoraproject Fedora — versions 33, 34
- N/a — versions n/a
Weakness classification (CWE)
Public proof-of-concept exploits
References
- cve@mitre.org (x_refsource_MISC, Mitigation, Vendor Advisory)
- cve@mitre.org (x_refsource_MISC, Mitigation, Vendor Advisory)
- cve@mitre.org (Patch, Third Party Advisory, x_refsource_MISC)
- cve@mitre.org (Patch, Third Party Advisory, x_refsource_MISC)
- cve@mitre.org (x_refsource_FEDORA, vendor-advisory)
- cve@mitre.org (x_refsource_FEDORA, vendor-advisory)
- cve@mitre.org (vendor-advisory, Third Party Advisory, x_refsource_DEBIAN)
Frequently asked questions
- What is CVE-2021-36740?
- CVE-2021-36740 is a medium-severity vulnerability in Varnish-Cache Varnish Cache, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 6.5/10. Published 2021-07-14.
- How severe is CVE-2021-36740?
- Medium severity. CVSS v3 base score is 6.5 out of 10.
- Is CVE-2021-36740 known to be exploited?
- 15 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.