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CVE-2021-28652

20
FAUCET Score

CVE-2021-28652 describes a Denial of Service (DoS) vulnerability in Squid versions before 4.15 and 5.x before 5.0.6, affecting various Debian and Fedora distributions. This flaw, due to incorrect parser validation, allows a trusted client with Cache Manager API access to trigger memory leaks, eventually leading to a DoS. Rated as Medium severity (CVSS 4.9), the attack requires high privileges and has a high impact on availability, but no impact on confidentiality or integrity. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
>= 1.0, < 4.15CPE matchmatch criteria
cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*
>= 5.0, < 5.0.6CPE matchmatch criteria
cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
33CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

4.9MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
1.2
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
4.34%
Probability of exploitation in next 30 days
EPSS Percentile
90.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0434 is in the 98th percentile among its peer group of 3,565 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: squid:4-8050020210618131503.b4937e53
View patch

Vendor Advisories (1)

redhatCVE-2021-28652Moderate

squid: denial of service issue in Cache Manager

May 10, 2021

References

bugs.squid-cache.org / show_bug.cgi
ExploitIssue TrackingVendor Advisory
seclists.org / fulldisclosure/2023/Oct/14
Mailing ListThird Party Advisory
github.com / squid-cache/squid/security/advisories/GHSA-m47m-9hvw-7447
PatchThird Party Advisory
lists.debian.org / debian-lts-announce/2021/06/msg00014.html
Mailing ListThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/LSQ3U54ZCNXR44QRPW3AV2VCS6K3TKCF
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/T4EPIWUZDJAXADDHVOPKRBTQHPBR6H66
debian.org / security/2021/dsa-4924
Third Party Advisory
openwall.com / lists/oss-security/2023/10/11/3
Mailing ListThird Party Advisory