Squid Web Proxy up to 4.14/5.0.5 Range Request denial of service

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.
5.1$0-$5k0.00

Summaryinfo

A vulnerability described as problematic has been identified in Squid Web Proxy up to 4.14/5.0.5. This affects an unknown function of the component Range Request Handler. Such manipulation leads to denial of service. This vulnerability is traded as CVE-2021-31806. The attack may be launched remotely. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Squid Web Proxy up to 4.14/5.0.5 (Firewall Software) and classified as problematic. Affected by this issue is an unknown code block of the component Range Request Handler. The manipulation with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. Impacted is availability.

The weakness was shared 05/28/2021. The advisory is shared for download at github.com. This vulnerability is handled as CVE-2021-31806. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1499.

The vulnerability scanner Nessus provides a plugin with the ID 275771 (Oracle Linux 7 : squid (ELSA-2025-19167)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 4.15 or 5.0.6 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at squid-cache.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (275771). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.3
VulDB Meta Temp Score: 5.1

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

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

Exploitinginfo

Class: Denial of service
CWE: CWE-404
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

Nessus ID: 275771
Nessus Name: Oracle Linux 7 : squid (ELSA-2025-19167)

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Upgrade: Web Proxy 4.15/5.0.6
Patch: squid-cache.org

Timelineinfo

04/26/2021 🔍
05/28/2021 +32 days 🔍
05/28/2021 +0 days 🔍
11/20/2025 +1637 days 🔍

Sourcesinfo

Vendor: squid-cache.org

Advisory: github.com
Status: Confirmed

CVE: CVE-2021-31806 (🔍)
GCVE (CVE): GCVE-0-2021-31806
GCVE (VulDB): GCVE-100-175964

Entryinfo

Created: 05/28/2021 06:22
Updated: 11/20/2025 02:14
Changes: 05/28/2021 06:22 (40), 05/30/2021 11:00 (5), 11/20/2025 02:14 (16)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Interested in the pricing of exploits?

See the underground prices here!