Heap-based Buffer Overflow in FreeBSD Kernel Core Dump

Executive Summary

This vulnerability is a race condition in FreeBSD's ELF core dump mechanism. The kernel counts memory regions to dump, allocates a buffer for program headers, then populates them in a second pass. A malicious process sharing the address space via rfork(2) can modify the memory map between these passes, causing the second pass to write program headers past the allocated buffer. This results in an out-of-bounds write on the kernel heap.

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Detection Guidance

Detecting this vulnerability requires checking if your FreeBSD system is running a vulnerable kernel version. Run uname -a to check the kernel version and compare it against the patched versions listed in the advisory. Additionally, check if core dumps are enabled by running sysctl kern.coredump.

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Impact Analysis

An unprivileged local user sharing an address space with a process that dumps core could exploit this to trigger a kernel heap out-of-bounds write. This may lead to privilege escalation, allowing the attacker to gain elevated system access.

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Compliance Impact

This vulnerability primarily affects system integrity and access control, which are relevant to compliance with standards like GDPR and HIPAA. A successful exploit could allow privilege escalation, potentially granting unauthorized access to sensitive data. This could violate confidentiality requirements under GDPR and HIPAA, leading to non-compliance if exploited.

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Mitigation Strategies

Immediately upgrade your FreeBSD system to a patched version using pkg, freebsd-update, or apply source code patches as described in the advisory. As a temporary workaround, disable core dumps by setting sysctl kern.coredump=0.

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