CVE-2021-33620
squid: Squid before 4.15 and 5.x before 5.0.6 allows remote servers to cause adenial of service (affecting availability to a...
CVE-2021-33620 is fixed in 9 products on 1 platform, first by squid 3.5.27-1ubuntu1.11, released May 28, 2021. It is not reported as exploited. Patch Radar priority: High.
High
CVSS
7.4
Medium
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.7958
99th percentile
Squid before 4.15 and 5.x before 5.0.6 allows remote servers to cause adenial of service (affecting availability to all clients) via an HTTPresponse. The issue trigger is a header that can be expected to exist inHTTP traffic without any malicious intent by the server.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| libecap · RHEL 8 | 0:1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2021:4292 | Nov 9, 2021 |
| libecap · almalinux 8 | 1.0.1-2.module_el8.6.0+2741+01592ae8 | ALSA-2021:4292 | Nov 9, 2021 |
| libecap · ol 8 | 0:1.0.1-2.module+el8.3.0+7819+eb7d4ef6 | ELSA-2021-4292 | Nov 16, 2021 |
| libecap · rocky 8 | 0:1.0.1-2.module+el8.4.0+404+316a0dc5 | RLSA-2021:4292 | Nov 9, 2021 |
| libecap-devel · RHEL 8 | 0:1.0.1-2.module+el8.1.0+4044+36416a77 | RHSA-2021:4292 | Nov 9, 2021 |
| libecap-devel · almalinux 8 | 1.0.1-2.module_el8.6.0+2741+01592ae8 | ALSA-2021:4292 | Nov 9, 2021 |
| libecap-devel · ol 8 | 0:1.0.1-2.module+el8.3.0+7819+eb7d4ef6 | ELSA-2021-4292 | Nov 16, 2021 |
| squid · RHEL 8 | 7:4.15-1.module+el8.5.0+11469+24c223d9 | RHSA-2021:4292 | Nov 9, 2021 |
| squid · Ubuntu 18.04.6 LTS (bionic) | 3.5.27-1ubuntu1.11 | squid 3.5.27-1ubuntu1.11 | May 28, 2021 |
| squid · Ubuntu 20.04 LTS (focal) | 4.10-1ubuntu1.4 | squid 4.10-1ubuntu1.4 | May 28, 2021 |
| squid · Ubuntu 24.10 (oracular) | 4.13-10ubuntu1 | squid 4.13-10ubuntu1 | Jan 16, 2026 |
| squid · Ubuntu 25.04 (plucky) | 4.13-10ubuntu1 | squid 4.13-10ubuntu1 | Jan 16, 2026 |
| squid · almalinux 8 | 7:4.15-3.module_el8.6.0+3010+383bc947.1 | ALSA-2021:4292 | Nov 9, 2021 |
| squid · ol 8 | 7:4.15-1.module+el8.5.0+20327+24c223d9 | ELSA-2021-4292 | Nov 16, 2021 |
| squid · rocky 8 | 7:4.15-1.module+el8.5.0+705+218dec94 | RLSA-2021:4292 | Nov 9, 2021 |
| squid-cgi · Ubuntu 18.04.6 LTS (bionic) | 3.5.27-1ubuntu1.11 | squid-cgi 3.5.27-1ubuntu1.11 | May 28, 2021 |
| squid-cgi · Ubuntu 20.04 LTS (focal) | 4.10-1ubuntu1.4 | squid-cgi 4.10-1ubuntu1.4 | May 28, 2021 |
| squid-cgi · Ubuntu 24.10 (oracular) | 4.13-10ubuntu1 | squid-cgi 4.13-10ubuntu1 | Jan 16, 2026 |
| squid-cgi · Ubuntu 25.04 (plucky) | 4.13-10ubuntu1 | squid-cgi 4.13-10ubuntu1 | Jan 16, 2026 |
| squid-common · Ubuntu 18.04.6 LTS (bionic) | 3.5.27-1ubuntu1.11 | squid-common 3.5.27-1ubuntu1.11 | May 28, 2021 |
| squid-common · Ubuntu 20.04 LTS (focal) | 4.10-1ubuntu1.4 | squid-common 4.10-1ubuntu1.4 | May 28, 2021 |
| squid-common · Ubuntu 24.10 (oracular) | 4.13-10ubuntu1 | squid-common 4.13-10ubuntu1 | Jan 16, 2026 |
| squid-common · Ubuntu 25.04 (plucky) | 4.13-10ubuntu1 | squid-common 4.13-10ubuntu1 | Jan 16, 2026 |
| squid-openssl · Ubuntu 24.10 (oracular) | 4.13-10ubuntu1 | squid-openssl 4.13-10ubuntu1 | Jan 16, 2026 |
| squid-openssl · Ubuntu 25.04 (plucky) | 4.13-10ubuntu1 | squid-openssl 4.13-10ubuntu1 | Jan 16, 2026 |
| squid-purge · Ubuntu 18.04.6 LTS (bionic) | 3.5.27-1ubuntu1.11 | squid-purge 3.5.27-1ubuntu1.11 | May 28, 2021 |
| squid-purge · Ubuntu 20.04 LTS (focal) | 4.10-1ubuntu1.4 | squid-purge 4.10-1ubuntu1.4 | May 28, 2021 |
| squid-purge · Ubuntu 24.10 (oracular) | 4.13-10ubuntu1 | squid-purge 4.13-10ubuntu1 | Jan 16, 2026 |
| squid-purge · Ubuntu 25.04 (plucky) | 4.13-10ubuntu1 | squid-purge 4.13-10ubuntu1 | Jan 16, 2026 |
| squid3 · Ubuntu 18.04.6 LTS (bionic) | 3.5.27-1ubuntu1.11 | squid3 3.5.27-1ubuntu1.11 | May 28, 2021 |
| squidclient · Ubuntu 18.04.6 LTS (bionic) | 3.5.27-1ubuntu1.11 | squidclient 3.5.27-1ubuntu1.11 | May 28, 2021 |
| squidclient · Ubuntu 20.04 LTS (focal) | 4.10-1ubuntu1.4 | squidclient 4.10-1ubuntu1.4 | May 28, 2021 |
| squidclient · Ubuntu 24.10 (oracular) | 4.13-10ubuntu1 | squidclient 4.13-10ubuntu1 | Jan 16, 2026 |
| squidclient · Ubuntu 25.04 (plucky) | 4.13-10ubuntu1 | squidclient 4.13-10ubuntu1 | Jan 16, 2026 |
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