CVE-2021-28652
squid: denial of service issue in Cache Manager
Severity
ModerateRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · May 10, 2021
Updated · November 22, 2025
Description
A flaw was found in Squid. A parser validation bug could allow a trusted client with Cache Manager API access privileges to trigger memory leaks, potentially resulting in a denial of service against Squid. The highest threat from this vulnerability is to system availability.
Statement
This issue has been rated as having a security impact of Moderate. At this stage in their life, Red Hat Enterprise Linux 6 and 7 only accept Important and Critical Security Advisories (RHSAs) and this flaw does not meet these criteria. For additional information, refer to the Red Hat Enterprise Linux Life Cycle: https://access.redhat.com/support/policy/updates/errata.
Red Hat Satellite does not ship the Squid package, however, does consume it from RHEL 7 repository. Product is not affected by this flaw as squid.conf configuration disables all the http_access fragments except the localhost.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
To mitigate this flaw Cache Manager access privileges can be hardened, for example by requiring authentication or other access controls in the "http_access" directive beyond the default IP address restriction. Alternatively, Cache Manager access can be disabled entirely if not needed. To do so, place the following line in squid.conf before lines containing "allow" :
http_access deny manager
CVSS / CWE
CVSS 3.1 · 6.8CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H
CWE-401 · Missing Release of Memory after Effective Lifetime