Semaphore Set Size Validation Bypass in FreeBSD Kernel

Executive Summary

This is a heap out-of-bounds access vulnerability in the semctl(2) system call in FreeBSD. It occurs due to a sequence-number wrap-around in the GETALL and SETALL commands. An attacker can rapidly destroy and recreate semaphore sets to cause the sequence number to wrap, bypassing validation checks. This allows out-of-bounds reads and writes in kernel heap memory.

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Detection Guidance

This vulnerability is specific to FreeBSD systems and requires local access to exploit. Detection primarily involves checking if your FreeBSD system is running a vulnerable kernel version. Use the command 'freebsd-version' to check your current version. Compare it against the patched versions mentioned in the advisory.

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Impact Analysis

An unprivileged local user can exploit this to trigger out-of-bounds memory access in the kernel. This could lead to privilege escalation, allowing the attacker to gain higher system privileges than intended.

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Compliance Impact

This vulnerability primarily impacts system integrity and confidentiality by allowing local privilege escalation through kernel heap memory corruption. While not directly targeting data processing or storage, successful exploitation could lead to unauthorized system access, which may indirectly affect compliance with standards like GDPR or HIPAA by compromising data protection controls.

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Mitigation Strategies

Immediately update your FreeBSD system using pkg(8), freebsd-update(8), or apply source code patches as recommended in the advisory. After updating, reboot the system to ensure the changes take effect. No workaround is available, so updating is the only mitigation.

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