Squid Web Proxy up to 4.14/5.0.5 WCCP Protocol out-of-bounds

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.
4.5$0-$5k0.00

Summaryinfo

A vulnerability was found in Squid Web Proxy up to 4.14/5.0.5. It has been classified as problematic. The impacted element is an unknown function of the component WCCP Protocol Handler. The manipulation leads to out-of-bounds. This vulnerability is listed as CVE-2021-28116. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Squid Web Proxy up to 4.14/5.0.5 (Firewall Software). This issue affects an unknown code block of the component WCCP Protocol Handler. The manipulation with an unknown input leads to a out-of-bounds vulnerability. Using CWE to declare the problem leads to CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality.

The weakness was presented 03/10/2021. It is possible to read the advisory at zerodayinitiative.com. The identification of this vulnerability is CVE-2021-28116. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/20/2025).

The vulnerability scanner Nessus provides a plugin with the ID 252913 (Linux Distros Unpatched Vulnerability : CVE-2021-28116), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at Tenable (252913). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

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Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.5
VulDB Meta Temp Score: 4.5

VulDB Base Score: 3.7
VulDB Temp Score: 3.7
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 5.3
NVD Vector: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Out-of-bounds
CWE: CWE-125 / CWE-119
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Nessus ID: 252913
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2021-28116

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔍

Timelineinfo

03/09/2021 🔍
03/10/2021 +1 days 🔍
03/10/2021 +0 days 🔍
08/20/2025 +1624 days 🔍

Sourcesinfo

Vendor: squid-cache.org

Advisory: zerodayinitiative.com
Status: Not defined
Confirmation: 🔍

CVE: CVE-2021-28116 (🔍)
GCVE (CVE): GCVE-0-2021-28116
GCVE (VulDB): GCVE-100-170903

Entryinfo

Created: 03/10/2021 10:06
Updated: 08/20/2025 19:12
Changes: 03/10/2021 10:06 (38), 03/29/2021 19:12 (2), 03/29/2021 19:19 (19), 08/20/2025 19:12 (16)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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