Critical Denial of Service Vulnerability in Squid Proxy Server
Summary
ALSA-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 protocols such as FTP and HTTP. It is widely used to improve web performance by caching frequently accessed content, reducing bandwidth usage, and enhancing response times. However, Squid is susceptible to specific vulnerabilities that can lead to service disruptions, making it essential for users to stay informed about security updates.
Vulnerability Detail
The vulnerability arises from a heap Use-After-Free issue in the Internet Cache Protocol (ICP) handling within Squid. This flaw can be exploited by attackers to craft specific ICP traffic that triggers a Denial of Service (DoS) condition, potentially leading to service outages. The vulnerabilities identified as CVE-2026-33526 and CVE-2026-32748 pose significant risks, as they can be exploited remotely without authentication, affecting the availability of the Squid server.
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 measure, users can restrict access to the Squid server by implementing firewall rules to limit incoming ICP traffic until the package is updated. This can be done by configuring the firewall to block specific ports used by ICP.
Conclusion
The identified vulnerabilities in the Squid proxy server pose significant risks of Denial of Service attacks. It is crucial for users to update their Squid installations to the latest patched version to ensure the security and availability of their services. Additionally, temporary workarounds can be employed to mitigate risks until updates are applied.
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FAQ
The vulnerabilities are related to Denial of Service attacks that can be triggered through crafted ICP traffic.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without any signup.
The vulnerabilities are documented under CVE-2026-32748 and CVE-2026-33526.
Yes, a patch is available in the updated version of the Squid package, specifically version 7:6.10-6.el10_1.3.
If immediate updates are not possible, consider implementing firewall rules to restrict access to the Squid server as a temporary workaround.
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