CVE-2021-33620

Squid before 4.15 and 5.x before 5.0.6 allows remote servers to cause a denial of service (affecting availability to all clients) via an HTTP response. The issue trigger is a header that can be expected to exist in HTTP traffic without any malicious intent by the server.

• CWE-20

• http://seclists.org/fulldisclosure/2023/Oct/14Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2023/10/11/3Mailing List, Third Party Advisory
• http://www.squid-cache.org/Versions/v4/changesets/squid-4-1e05a85bd28c22c9ca5d3ac9f5e86d6269ec0a8c.patchMailing List, Patch, Vendor Advisory
• http://www.squid-cache.org/Versions/v5/changesets/squid-5-8af775ed98bfd610f9ce762fe177e01b2675588c.patchMailing List, Patch, Vendor Advisory
• https://github.com/squid-cache/squid/security/advisories/GHSA-572g-rvwr-6c7fPatch, Third Party Advisory
• https://lists.debian.org/debian-lts-announce/2021/06/msg00014.htmlMailing List, Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LSQ3U54ZCNXR44QRPW3AV2VCS6K3TKCF/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T4EPIWUZDJAXADDHVOPKRBTQHPBR6H66/
• http://seclists.org/fulldisclosure/2023/Oct/14Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2023/10/11/3Mailing List, Third Party Advisory
• http://www.squid-cache.org/Versions/v4/changesets/squid-4-1e05a85bd28c22c9ca5d3ac9f5e86d6269ec0a8c.patchMailing List, Patch, Vendor Advisory
• http://www.squid-cache.org/Versions/v5/changesets/squid-5-8af775ed98bfd610f9ce762fe177e01b2675588c.patchMailing List, Patch, Vendor Advisory
• https://github.com/squid-cache/squid/security/advisories/GHSA-572g-rvwr-6c7fPatch, Third Party Advisory
• https://lists.debian.org/debian-lts-announce/2021/06/msg00014.htmlMailing List, Third Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LSQ3U54ZCNXR44QRPW3AV2VCS6K3TKCF/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T4EPIWUZDJAXADDHVOPKRBTQHPBR6H66/

Published

May 28, 2021

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
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• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

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