CVE-2021-28651
squid: denial of service in URN processing
Severity
ModerateRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · May 10, 2021
Updated · June 27, 2026
Description
An input validation flaw was found in Squid. This issue could allow a malicious server in collaboration with a trusted client to consume arbitrarily large amounts of memory on the server running 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
If possible, disable URN processing by adding the following lines in squid.conf:
acl URN proto URN
http_access deny URN
CVSS / CWE
CVSS 3.1 · 7.4CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:H
CWE-770 · Allocation of Resources Without Limits or Throttling