# CVE-2021-36740: varnish: Varnish Cache is a high-performance HTTP accelerator

CVE-2021-36740 is fixed in 5 products on 1 platform, first by RHSA-2021:2988, released August 2, 2021. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-36740
- Priority: High
- CVSS: 8.1 (Important)
- EPSS: 0.0160
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 14, 2021

## Description

Varnish Cache is a high-performance HTTP accelerator. It stores web pages in memory so web servers don't have to create the same web page over and over again, giving the website a significant speed up.  Security Fix(es):  * varnish: HTTP/2 request smuggling attack via a large Content-Length header for a POST request (CVE-2021-36740)  For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libvarnishapi2 Ubuntu 20.04 LTS (focal) | 6.2.1-2ubuntu0.1 | [libvarnishapi2 6.2.1-2ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libvarnishapi2-6.2.1-2ubuntu0.1.md) | Jan 25, 2022 |
| Linux | varnish Debian 11.6 (bullseye) | 6.5.1-1+deb11u2 | [DSA-5088-1](https://patchblox.com/security/data/fix/linux/dsa-5088-1.md) | Mar 3, 2022 |
| Linux | varnish RHEL 8 | 0:6.0.6-2.module+el8.4.0+11921+1a6539fc.1 | [RHSA-2021:2988](https://patchblox.com/security/data/fix/linux/rhsa-2021-2988.md) | Aug 2, 2021 |
| Linux | varnish Ubuntu 20.04 LTS (focal) | 6.2.1-2ubuntu0.1 | [varnish 6.2.1-2ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-varnish-6.2.1-2ubuntu0.1.md) | Jan 25, 2022 |
| Linux | varnish ol 8 | 0:6.0.6-2.module+el8.4.0+20258+f99218b2.1 | [ELSA-2021-2988](https://patchblox.com/security/data/fix/linux/elsa-2021-2988.md) | Aug 3, 2021 |
| Linux | varnish-devel RHEL 8 | 0:6.0.6-2.module+el8.4.0+11921+1a6539fc.1 | [RHSA-2021:2988](https://patchblox.com/security/data/fix/linux/rhsa-2021-2988.md) | Aug 2, 2021 |
| Linux | varnish-devel ol 8 | 0:6.0.6-2.module+el8.4.0+20258+f99218b2.1 | [ELSA-2021-2988](https://patchblox.com/security/data/fix/linux/elsa-2021-2988.md) | Aug 3, 2021 |
| Linux | varnish-docs RHEL 8 | 0:6.0.6-2.module+el8.4.0+11921+1a6539fc.1 | [RHSA-2021:2988](https://patchblox.com/security/data/fix/linux/rhsa-2021-2988.md) | Aug 2, 2021 |
| Linux | varnish-docs ol 8 | 0:6.0.6-2.module+el8.4.0+20258+f99218b2.1 | [ELSA-2021-2988](https://patchblox.com/security/data/fix/linux/elsa-2021-2988.md) | Aug 3, 2021 |
| Linux | varnish-modules RHEL 8 | 0:0.15.0-5.module+el8.3.0+6843+b3b42fcc | [RHSA-2021:2988](https://patchblox.com/security/data/fix/linux/rhsa-2021-2988.md) | Aug 2, 2021 |
| Linux | varnish-modules ol 8 | 0:0.15.0-5.module+el8.3.0+7653+45014445 | [ELSA-2021-2988](https://patchblox.com/security/data/fix/linux/elsa-2021-2988.md) | Aug 3, 2021 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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