Race Condition in FreeBSD SUID Binary Memory Access

Executive Summary

This is a local privilege escalation vulnerability affecting FreeBSD. It involves a race condition in the execve(2) system call when handling SUID binaries. The kernel installs the new virtual address space before updating process credentials, creating a window where an unprivileged local user can access and modify the target process's memory via procfs or linprocfs. This allows the attacker to gain full control of the system.

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Detection Guidance

Detecting this vulnerability requires checking if your FreeBSD system is running a vulnerable version. Use the following commands to check your FreeBSD version and patch status: uname -a to display the system version, pkg audit -F to check for vulnerable packages, and freebsd-version to confirm the installed patch level. Compare the output against the patched versions mentioned in the advisory.

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Impact Analysis

An unprivileged local user could exploit this to gain full control of an affected FreeBSD system. This means attackers could escalate privileges, install malware, steal data, or perform other malicious actions on the system.

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Compliance Impact

This vulnerability could lead to unauthorized access to sensitive process memory, potentially exposing personal or health data. Compliance with GDPR or HIPAA may be impacted if such data is accessed or exfiltrated due to insufficient process isolation during privilege escalation.

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Mitigation Strategies

Immediately upgrade your FreeBSD system to a patched version using pkg update && pkg upgrade or freebsd-update fetch install followed by a system reboot. If source code patches are available, apply them and rebuild the kernel. Since no workaround exists, upgrading is the only mitigation. Verify the patch status after reboot using uname -a or freebsd-version.

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