Critical Denial of Service Vulnerabilities in Squid Proxy Server
Summary
ALSA-2026:6301: Important: squid security update. Affects squid versions < 7:5.5-22.el9_7.4. Fixed in 7:5.5-22.el9_7.4. How to fix ↓
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Habilume
Habit tracker with a companion that grows with you
Complete habits, earn Lume Points, and watch your Lume grow as you stay consistent.
Background
Squid is a high-performance proxy caching server widely used for web clients, supporting various data objects including FTP and HTTP. It is designed to enhance web performance by caching frequently accessed content, reducing bandwidth usage, and improving response times. However, like any software, Squid can be susceptible to security vulnerabilities that may compromise its functionality and the systems it serves.
Vulnerability Detail
The vulnerabilities identified in Squid include a Denial of Service (DoS) caused by a heap Use-After-Free issue in ICP handling (CVE-2026-33526) and another DoS vulnerability triggered by crafted ICP traffic (CVE-2026-32748). These vulnerabilities can lead to service interruptions, making the server unresponsive to legitimate requests, thereby affecting users and applications relying on it.
How To Fix
Minimum fixed version
7:5.5-22.el9_7.4
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, you may consider disabling ICP traffic until the patch is applied. This can be done by modifying the Squid configuration file (usually located at /etc/squid/squid.conf) and commenting out or removing any lines related to ICP.
Conclusion
The identified vulnerabilities in Squid pose significant risks, including Denial of Service attacks that can disrupt service availability. It is crucial to update to the patched version to protect your systems. Additionally, utilizing tools like Vulert can help monitor and manage vulnerabilities effectively.
See every vulnerability recorded for squid →
FAQ
The vulnerabilities can lead to Denial of Service, causing the Squid server to become unresponsive and affecting all users relying on it.
You can use Vulert to monitor and alert for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected without any signup.
A Use-After-Free vulnerability occurs when a program continues to use a pointer after the memory it points to has been freed, potentially leading to arbitrary code execution or crashes.
Yes, you can temporarily disable ICP traffic in the Squid configuration to mitigate the risk until the patch is applied.
More details can be found on the CVE pages for CVE-2026-32748 and CVE-2026-33526, which provide in-depth information about the vulnerabilities and their impacts.
Related vulnerabilities
Recent vulnerabilities recorded for squid.
Habilume
Habit tracker with a companion that grows with you
Complete habits, earn Lume Points, and watch your Lume grow as you stay consistent.
Follow Vulert in Google
Get more Vulert vulnerability and dependency-security updates in Google Search and AI results.