Squid Proxy 3.5.17/4.0.9 HTTP Request data authenticity

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.

A vulnerability has been found in Squid Proxy 3.5.17/4.0.9 (Firewall Software) and classified as critical. Affected by this vulnerability is an unknown code of the component HTTP Request Handler. The manipulation with an unknown input leads to a data authenticity vulnerability. The CWE definition for the vulnerability is CWE-345. The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

client_side.cc in Squid before 3.5.18 and 4.x before 4.0.10 does not properly ignore the Host header when absolute-URI is provided, which allows remote attackers to conduct cache-poisoning attacks via an HTTP request.

The weakness was presented 05/06/2016 as SQUID-2016:7 as confirmed advisory (Website). The advisory is shared at squid-cache.org. This vulnerability is known as CVE-2016-4553 since 05/06/2016. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 91393 (CentOS 6 : squid34 (CESA-2016:1140)), which helps to determine the existence of the flaw in a target environment. It is assigned to the family CentOS Local Security Checks and running in the context l. The commercial vulnerability scanner Qualys is able to test this issue with plugin 236019 (Red Hat Update for Squid 3.4 (RHSA-2016:1140)).

Upgrading to version 3.5.18 or 4.0.10 eliminates this vulnerability. A possible mitigation has been published immediately after the disclosure of the vulnerability.

The vulnerability is also documented in the databases at X-Force (113041) and Tenable (91393). See 82766, 82767, 82768 and 82769 for similar entries.







CPE 2.3info

CPE 2.2info


VulDB CVSS-B Score: 🔍
VulDB CVSS-BT Score: 🔍
VulDB Vector: 🔍
VulDB Reliability: 🔍


VulDB Meta Base Score: 8.7
VulDB Meta Temp Score: 8.1

VulDB Base Score: 8.8
VulDB Temp Score: 7.7
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 8.6
NVD Vector: 🔍



VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍


Class: Data authenticity
CWE: CWE-345
ATT&CK: Unknown

Local: No
Remote: Yes

Availability: 🔍
Status: Unproven

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍


Nessus ID: 91393
Nessus Name: CentOS 6 : squid34 (CESA-2016:1140)
Nessus File: 🔍
Nessus Risk: 🔍
Nessus Family: 🔍
Nessus Context: 🔍

OpenVAS ID: 841482
OpenVAS Name: Squid Cache Poisoning Vulnerability-01 May16 (Windows)
OpenVAS File: 🔍
OpenVAS Family: 🔍

Qualys ID: 🔍
Qualys Name: 🔍

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍


Recommended: Upgrade
Status: 🔍

Reaction Time: 🔍
0-Day Time: 🔍
Exposure Time: 🔍

Upgrade: Proxy 3.5.18/4.0.10


05/06/2016 🔍
05/06/2016 +0 days 🔍
05/06/2016 +0 days 🔍
05/10/2016 +4 days 🔍
05/10/2016 +0 days 🔍
06/01/2016 +22 days 🔍
08/18/2022 +2269 days 🔍


Vendor: squid-cache.org

Advisory: SQUID-2016:7
Status: Confirmed
Confirmation: 🔍

CVE: CVE-2016-4553 (🔍)
X-Force: 113041 - SQUID HTTP request security bypass
SecurityTracker: 1035768

See also: 🔍


Created: 05/10/2016 10:39 AM
Updated: 08/18/2022 07:29 AM
Changes: 05/10/2016 10:39 AM (70), 11/23/2018 10:46 AM (9), 08/18/2022 07:29 AM (4)
Complete: 🔍


No comments yet. Languages: en.

Please log in to comment.

Do you know our Splunk app?

Download it now for free!