// For flags

CVE-2021-28662

squid: denial of service in HTTP response processing

Severity Score

6.5
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

An issue was discovered in Squid 4.x before 4.15 and 5.x before 5.0.6. If a remote server sends a certain response header over HTTP or HTTPS, there is a denial of service. This header can plausibly occur in benign network traffic.

Se detectó un problema en Squid versiones 4.x anteriores a 4.15 y versiones 5.x anteriores a 5.0.6. Si un servidor remoto envía un determinado encabezado de respuesta por medio de HTTP o HTTPS, ocurre una denegación de servicio. Este encabezado puede ocurrir plausiblemente en tráfico de red benigno

An input validation flaw was found in Squid. This issue could allow a remote server to perform a denial of service against all clients using the proxy when delivering HTTP response messages. The highest threat from this vulnerability is to system availability.

Joshua Rogers discovered that Squid incorrectly handled requests with the urn: scheme. A remote attacker could possibly use this issue to cause Squid to consume resources, leading to a denial of service. Joshua Rogers discovered that Squid incorrectly handled requests to the Cache Manager API. A remote attacker with access privileges could possibly use this issue to cause Squid to consume resources, leading to a denial of service. This issue was only addressed in Ubuntu 20.04 LTS, Ubuntu 20.10, and Ubuntu 21.04. Various other issues were also addressed.

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Attack Vector
Network
Attack Complexity
Medium
Authentication
None
Confidentiality
None
Integrity
None
Availability
Partial
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2021-03-18 CVE Reserved
  • 2021-05-26 CVE Published
  • 2024-08-03 CVE Updated
  • 2025-03-30 EPSS Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-20: Improper Input Validation
  • CWE-116: Improper Encoding or Escaping of Output
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Squid-cache
Search vendor "Squid-cache"
 Squid
Search vendor "Squid-cache" for product "Squid"
 >= 4.0.1 < 4.15
Search vendor "Squid-cache" for product "Squid" and version " >= 4.0.1 < 4.15"
-
Affected
Squid-cache
Search vendor "Squid-cache"
 Squid
Search vendor "Squid-cache" for product "Squid"
 >= 5.0 < 5.0.6
Search vendor "Squid-cache" for product "Squid" and version " >= 5.0 < 5.0.6"
-
Affected
Debian
Search vendor "Debian"
 Debian Linux
Search vendor "Debian" for product "Debian Linux"
 10.0
Search vendor "Debian" for product "Debian Linux" and version "10.0"
-
Affected
Fedoraproject
Search vendor "Fedoraproject"
 Fedora
Search vendor "Fedoraproject" for product "Fedora"
 33
Search vendor "Fedoraproject" for product "Fedora" and version "33"
-
Affected
Fedoraproject
Search vendor "Fedoraproject"
 Fedora
Search vendor "Fedoraproject" for product "Fedora"
 34
Search vendor "Fedoraproject" for product "Fedora" and version "34"
-
Affected