Critical Denial of Service Vulnerability in Squid Proxy Server
Summary
RLSA-2026:8119: Important: squid security update. Affects squid versions < 7:6.10-6.el10_1.3. Fixed in 7:6.10-6.el10_1.3. How to fix ↓
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Background
Squid is a high-performance proxy caching server designed for web clients, supporting both FTP and HTTP data objects. It is widely used to improve web performance by caching frequently requested resources, reducing bandwidth usage, and enhancing response times. However, Squid is susceptible to certain vulnerabilities that can lead to service disruptions, particularly in its handling of Internet Cache Protocol (ICP) traffic.
Vulnerability Detail
The vulnerability arises from a heap Use-After-Free issue in the ICP handling of Squid, which can be exploited to cause a Denial of Service (DoS). Attackers can send crafted ICP traffic that triggers this vulnerability, leading to potential service outages. The affected CVEs are CVE-2026-32748 and CVE-2026-33526, both of which have a CVSS score of 7.5, indicating a high severity level. This vulnerability can severely impact the availability of the Squid service, making it critical for users to address it promptly.
How To Fix
Minimum fixed version
7:6.10-6.el10_1.3
This is the first release that contains the fix.
sudo dnf update squidTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, users can limit the exposure of their Squid server to untrusted networks or disable ICP handling if it is not necessary for their operations. This can be done by modifying the Squid configuration file (usually located at /etc/squid/squid.conf) and commenting out or removing the ICP-related directives.
Conclusion
The identified vulnerabilities in the Squid proxy server pose significant risks, particularly in terms of Denial of Service attacks. It is crucial for users to update their installations to the latest patched version to mitigate these risks. Additionally, employing temporary workarounds can help maintain service availability until updates can be applied.
See every vulnerability recorded for squid →
FAQ
The vulnerability can lead to a Denial of Service, causing the Squid server to become unresponsive and potentially disrupt services relying on it.
You can check your Squid version by running 'squid -v' in your terminal. If it is below the patched version (7:6.10-6.el10_1.3), it is vulnerable.
Yes, you can use Vulert, which monitors open-source vulnerabilities in your software using a manifest file like package-lock.json. You can check for vulnerabilities in your application without needing to install anything.
If an immediate update is not possible, consider implementing network restrictions to limit access to the Squid server or disabling ICP handling as a temporary measure.
For detailed information, refer to the CVE pages for CVE-2026-32748 and CVE-2026-33526, which provide insights into the vulnerabilities and their implications.
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