CVE-2023-6531 in Linux
Summary
by MITRE • 01/21/2024
A use-after-free flaw was found in the Linux Kernel due to a race problem in the unix garbage collector's deletion of SKB races with unix_stream_read_generic() on the socket that the SKB is queued on.
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Analysis
by VulDB Data Team • 07/26/2025
The vulnerability identified as CVE-2023-6531 represents a critical use-after-free flaw within the Linux kernel that stems from a race condition in the unix garbage collector's handling of socket buffer management. This issue specifically manifests when the garbage collector attempts to delete socket buffer (skb) entries while concurrent operations are occurring within the unix_stream_read_generic() function, creating a dangerous temporal overlap that can lead to memory corruption. The root cause lies in the improper synchronization mechanisms between the garbage collection process and the socket read operations, allowing for the possibility that freed memory structures may still be accessed by other kernel threads.
The technical implementation of this vulnerability involves the interaction between multiple kernel subsystems including the unix domain socket implementation, the socket buffer management system, and the garbage collection routines responsible for cleaning up unused socket resources. When a socket buffer is queued on a unix stream socket and simultaneously undergoes garbage collection while read operations are in progress, the kernel's memory management can result in a freed skb structure being accessed after deallocation. This race condition creates a scenario where attackers can potentially manipulate the kernel's memory layout to achieve arbitrary code execution or system compromise. The flaw operates at the kernel level and requires no privileged access to exploit, making it particularly dangerous in multi-user environments.
The operational impact of CVE-2023-6531 extends beyond simple memory corruption, as it can lead to system instability, denial of service conditions, or potential privilege escalation depending on the exploitation vector. The vulnerability affects systems running Linux kernel versions that contain the problematic unix socket garbage collection logic, with the risk being particularly high on systems that heavily utilize unix domain sockets for inter-process communication. Attackers can leverage this flaw to cause kernel crashes, create persistent backdoors, or gain elevated privileges within the operating system. The exploitation complexity is moderate to high, requiring precise timing and understanding of the kernel's memory management patterns, but the potential for system compromise makes this vulnerability a significant concern for system administrators and security professionals.
Mitigation strategies for CVE-2023-6531 should prioritize immediate kernel updates from trusted sources, as the primary fix involves patches that address the race condition in the unix garbage collector implementation. System administrators should also implement monitoring solutions to detect anomalous socket behavior patterns that might indicate exploitation attempts. Additional defensive measures include restricting unix domain socket usage where possible, implementing proper access controls, and maintaining comprehensive system logging for kernel-level activities. The vulnerability aligns with CWE-416, which addresses use-after-free errors, and could be categorized under ATT&CK technique T1068, involving exploit for privilege escalation, making it a critical target for both preventive and reactive security measures. Organizations should conduct thorough vulnerability assessments to identify systems running affected kernel versions and implement remediation plans promptly.