Vulnerability Monitor

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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.

Security Impact Summary

This vulnerability carries a MEDIUM severity rating with a CVSS v3.1 score of 6.5, indicating it can be exploited remotely over the network with relatively low complexity without requiring user interaction requiring only low-level privileges . The vulnerability impacts and availability (service disruption) for affected systems. Impacting 3 products from squid-cache, from fedoraproject, from debian organizations running these solutions should prioritize assessment and patching.

Historical Context

Reported in 2021, this vulnerability emerged during an era marked by increased sophistication in supply chain attacks, cloud infrastructure vulnerabilities, and software-as-a-service (SaaS) security challenges. Security practices during this period emphasized zero-trust architectures, container security, and API protection.

Published

2021-05-28T12:15:07.697

Last Modified

2024-11-21T06:09:12.380

Status

Modified

Source

[email protected]

Severity

CVSSv3.1: 6.5 (MEDIUM)

CVSSv2 Vector

AV:N/AC:L/Au:S/C:N/I:N/A:P

Access Vector: NETWORK
Access Complexity: LOW
Authentication: SINGLE
Confidentiality Impact: NONE
Integrity Impact: NONE
Availability Impact: PARTIAL

Exploitability Score

8.0

Impact Score

2.9

Weaknesses

Type: Primary
CWE-20

Affected Vendors & Products

Type	Vendor	Product	Version/Range	Vulnerable?
Application	squid-cache	squid	< 4.15	Yes
Application	squid-cache	squid	< 5.0.6	Yes
Operating System	fedoraproject	fedora	33	Yes
Operating System	fedoraproject	fedora	34	Yes
Operating System	debian	debian_linux	9.0	Yes

References

http://seclists.org/fulldisclosure/2023/Oct/14 Mailing List, Third Party Advisory ([email protected])
http://www.openwall.com/lists/oss-security/2023/10/11/3 Mailing List, Third Party Advisory ([email protected])
http://www.squid-cache.org/Versions/v4/changesets/squid-4-1e05a85bd28c22c9ca5d3ac9f5e86d6269ec0a8c.patch Mailing List, Patch, Vendor Advisory ([email protected])
http://www.squid-cache.org/Versions/v5/changesets/squid-5-8af775ed98bfd610f9ce762fe177e01b2675588c.patch Mailing List, Patch, Vendor Advisory ([email protected])
https://github.com/squid-cache/squid/security/advisories/GHSA-572g-rvwr-6c7f Patch, Third Party Advisory ([email protected])
https://lists.debian.org/debian-lts-announce/2021/06/msg00014.html Mailing List, Third Party Advisory ([email protected])
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LSQ3U54ZCNXR44QRPW3AV2VCS6K3TKCF/ ([email protected])
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T4EPIWUZDJAXADDHVOPKRBTQHPBR6H66/ ([email protected])
http://seclists.org/fulldisclosure/2023/Oct/14 Mailing List, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
http://www.openwall.com/lists/oss-security/2023/10/11/3 Mailing List, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
http://www.squid-cache.org/Versions/v4/changesets/squid-4-1e05a85bd28c22c9ca5d3ac9f5e86d6269ec0a8c.patch Mailing List, Patch, Vendor Advisory (af854a3a-2127-422b-91ae-364da2661108)
http://www.squid-cache.org/Versions/v5/changesets/squid-5-8af775ed98bfd610f9ce762fe177e01b2675588c.patch Mailing List, Patch, Vendor Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://github.com/squid-cache/squid/security/advisories/GHSA-572g-rvwr-6c7f Patch, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://lists.debian.org/debian-lts-announce/2021/06/msg00014.html Mailing List, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LSQ3U54ZCNXR44QRPW3AV2VCS6K3TKCF/ (af854a3a-2127-422b-91ae-364da2661108)
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T4EPIWUZDJAXADDHVOPKRBTQHPBR6H66/ (af854a3a-2127-422b-91ae-364da2661108)

How SecUtils Interprets This CVE

SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For squid-cache's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.