CVE-2021-28651

Name: CVE-2021-28651
Creator: NVD / NIST
Published: 2021-05-27T12:15:08.197+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 7.45%

Last modified Jun 17, 2026

CVE-2021-28651 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to a buffer-management bug, it allows a denial of service. EPSS estimates a 7.45% chance of exploitation in the next 30 days.

Description

An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to a buffer-management bug, it allows a denial of service. When resolving a request with the urn: scheme, the parser leaks a small amount of memory. However, there is an unspecified attack methodology that can easily trigger a large amount of memory consumption.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

7.45%

93.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-401

Affected Software

Vendor	Product	Versions
Squid-Cache	Squid	>= 2.0, < 4.15
Squid-Cache	Squid	>= 5.0, < 5.0.6
Debian	Debian Linux	9.0
Debian	Debian Linux	10.0
Fedoraproject	Fedora	33
Fedoraproject	Fedora	34
Netapp	Cloud Manager	All versions

References

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
https://bugs.squid-cache.org/show_bug.cgi?id=5104Exploit, Issue Tracking, Vendor Advisory
https://github.com/squid-cache/squid/security/advisories/GHSA-ch36-9jhx-phm4Patch, 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/
https://security.netapp.com/advisory/ntap-20210716-0007/Third Party Advisory
https://www.debian.org/security/2021/dsa-4924Third Party Advisory
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
https://bugs.squid-cache.org/show_bug.cgi?id=5104Exploit, Issue Tracking, Vendor Advisory
https://github.com/squid-cache/squid/security/advisories/GHSA-ch36-9jhx-phm4Patch, 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/
https://security.netapp.com/advisory/ntap-20210716-0007/Third Party Advisory
https://www.debian.org/security/2021/dsa-4924Third Party Advisory

Timeline

Published: May 27, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-28651?

How severe is CVE-2021-28651?

CVE-2021-28651 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 7.45% probability of exploitation in the next 30 days.

How do I fix CVE-2021-28651?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-28651?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST