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CVE-2021-28651

squid: denial of service in URN processing

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Severity

Moderate

Red Hat Product Security

7.4

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 · 7.4
CVSS: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