CVE-2023-53839: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-53839 is a data race vulnerability in the Linux kernel's DCCP (Datagram Congestion Control Protocol) subsystem, specifically around the dp->dccps_mss_cache field. The flaw exists because dccp_sendmsg() and do_dccp_getsockopt() both read dccps_mss_cache without proper synchronization before the socket lock is acquired, creating a classic TOCTOU-style data race condition. The vulnerability affects the Linux kernel from version 2.6.14 onward, with fixes backported to stable branches including 4.14.323, 4.19.292, 5.4.254, 5.10.191, 5.15.127, 6.1.46, 6.4.11, and 6.5+. It was published on December 9, 2025, and carries an estimated CVSS severity of Medium (Feedly, EUVD).

The root cause is a data race (CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization) in the Linux kernel's DCCP implementation. Specifically, dccp_sendmsg() reads the dp->dccps_mss_cache field prior to acquiring the socket lock, and do_dccp_getsockopt() exhibits the same unsynchronized read pattern. The fix adds READ_ONCE()/WRITE_ONCE() annotations to enforce memory ordering semantics and modifies dccp_sendmsg() to re-check dccps_mss_cache after the socket lock is held, eliminating the race window. Patches were applied across eight stable kernel branches (Feedly, EUVD).

The data race in the DCCP subsystem can lead to undefined behavior due to unsynchronized concurrent access to the dccps_mss_cache field, potentially resulting in incorrect MSS (Maximum Segment Size) values being used during socket operations. In practice, this could cause kernel instability, incorrect network behavior, or in edge cases, memory corruption depending on how the race manifests at runtime. The impact is generally limited to availability and integrity of DCCP socket operations on affected systems; there is no direct evidence of confidentiality breach or remote code execution stemming from this specific race (Feedly).

The Linux kernel maintainers have released fixes across multiple stable branches. Users should update to the following patched versions or later: 4.14.323, 4.19.292, 5.4.254, 5.10.191, 5.15.127, 6.1.46, 6.4.11, or 6.5+. Patches are available via the upstream stable kernel git repository. Distributions such as Amazon Linux 2 (ALAS2KERNEL-5.4-2025-116) and SUSE have also issued advisories incorporating these fixes. If upgrading is not immediately possible, disabling DCCP support on systems where it is not required (e.g., via kernel module blacklisting: echo 'install dccp /bin/true' >> /etc/modprobe.d/disable-dccp.conf) can reduce exposure (Feedly, Amazon ALAS).

Coverage of CVE-2023-53839 has been limited to routine security advisory channels, including Linux security aggregators and scanner vendors (Tenable, Qualys). SUSE issued kernel update advisories referencing this CVE. No notable researcher commentary or significant social media discussion has been identified (Feedly).