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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…
- 6.5MediumCVSS base score
- 1.6%Exploitation in 30 daysEPSS · top 24% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By mitre
Published
- 3 years later
· 3 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N |
- EPSS (exploitation in 30 days)
- 1.6% · top 24% of all CVEs (11 Nov 2026)
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.
Affected products
n/a
- affected n/a
References
References7
- https://varnish-cache.org/security/VSV00007.html (opens in a new tab)x_refsource_MISCx_transferred
- https://docs.varnish-software.com/security/VSV00007/ (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/varnishcache/varnish-cache/commit/9be22198e258d0e7a5c41f4291792214a29405cf (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/varnishcache/varnish-cache/commit/82b0a629f60136e76112c6f2c6372cce77b683be (opens in a new tab)x_refsource_MISCx_transferred
- FEDORA-2021-36e10d3f9f (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- FEDORA-2021-cf7585f0ca (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- DSA-5088 (opens in a new tab)vendor-advisoryx_refsource_DEBIANx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-23330 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-36740)Record last updated .