Integer Overflow Vulnerability in Linux Kernel (CVE-2026-90246)
Summary
DEBIAN-CVE-2026-90246: In the Linux kernel, the following vulnerability has been resolved: apparmor: fix integer overflow in verify_tags() bounds check verify_tags() validates the tagset table unpacked from a policy blob. Affects linux versions 6.12.100-1 – 7.2~rc7-1~exp1. No fix is published. How to fix ↓
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Background
The Linux kernel is the core component of many operating systems, providing essential services for hardware and software interaction. It is widely used in various distributions, including Debian. This vulnerability affects the AppArmor security module, which is designed to restrict program capabilities with per-program profiles. The specific issue arises from an integer overflow in the verify_tags() function, which can lead to out-of-bounds memory access.
Vulnerability Detail
In the Linux kernel, an integer overflow vulnerability has been identified in the verify_tags() function of the AppArmor module. This function is responsible for validating a tagset table unpacked from a policy blob. The vulnerability occurs when an attacker supplies a count close to the maximum value of a 32-bit unsigned integer (U32_MAX), causing the sum of the index and count to wrap around and bypass the bounds check. This can lead to an out-of-bounds read, potentially allowing an attacker to read sensitive data or crash the system. The vulnerability is particularly concerning as it can be exploited by unprivileged tasks within nested user namespaces, making it accessible to a wider range of attackers.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a temporary workaround, consider disabling AppArmor profiles or restricting the use of unprivileged user namespaces until the patch is applied. This can be done by modifying the AppArmor configuration files or using the command
sudo systemctl stop apparmor' to stop the service.
Conclusion
The CVE-2026-90246 vulnerability in the Linux kernel's AppArmor module poses a significant risk due to its potential for exploitation by unprivileged users. It is crucial to apply the necessary updates to protect your system from this and other vulnerabilities. Utilizing tools like Vulert can aid in monitoring for such issues in real-time.
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FAQ
CVE-2026-90246 is a vulnerability in the Linux kernel's AppArmor module that allows for potential out-of-bounds memory access due to an integer overflow in the verify_tags() function.
Any system running a vulnerable version of the Linux kernel with AppArmor enabled may be affected, particularly those using Debian-based distributions.
You can use tools like Vulert to monitor and alert for open-source vulnerabilities in your software. You can check your application against this vulnerability using the Vulert playground at Vulert Scanner.
Exploitation of this vulnerability could lead to unauthorized access to sensitive data, system crashes, or other malicious activities, especially from unprivileged users.
Yes, the permanent fix is to update the Linux kernel to a version that includes the patch for CVE-2026-90246. Regularly updating your system will help mitigate such vulnerabilities.
References
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