CVE-2025-68247: 
Linux Debian vulnerability analysis and mitigation

CVE-2025-68247 is a memory leak vulnerability in the Linux kernel's POSIX timer subsystem, specifically within the do_timer_create() function. When POSIX timer creation is configured to allocate a specific timer ID and a subsequent access to a user-space value faults, the function exits without freeing the already-allocated POSIX timer structure, resulting in a kernel memory leak. The vulnerability was published on December 16, 2025, and affects the Linux kernel. No CVSS score has been assigned by NVD at this time; the EPSS score is approximately 0.018% (Feedly, CVE Record).

The root cause is a missing memory deallocation path in do_timer_create() within the kernel's posix-timers subsystem (CWE not formally assigned by NVD). When a timer creation request specifies a particular timer ID, the kernel allocates a posix_timer structure before attempting to read the requested ID from user space. If the get_user() or equivalent user-space access faults (e.g., due to an invalid or unmapped user pointer), the function returns an error without freeing the previously allocated structure, leaking kernel memory. The fix moves the allocation to occur after the user-space access, eliminating the leak path. Patches are referenced at two stable kernel commits: e0fd4d42e27f and f417f44524e7 (kernel.org patch 1, kernel.org patch 2).

The primary impact of this vulnerability is a kernel memory leak, which can degrade system availability over time if repeatedly triggered. An attacker or unprivileged local user with the ability to invoke timer_create() syscalls with crafted arguments could cause gradual exhaustion of kernel memory, potentially leading to system instability or denial of service. There is no known direct path to privilege escalation, code execution, or data exfiltration from this vulnerability (Feedly).

No public proof-of-concept exploit code is known for CVE-2025-68247, and there is no evidence of in-the-wild exploitation. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. The EPSS score is approximately 0.018% (0.000180), indicating a very low probability of exploitation in the near term (Feedly). Exploitation would require local access to a vulnerable system and the ability to make timer_create() syscalls.

The fix has been applied to the Linux kernel stable tree via commits e0fd4d42e27f761e9cc82801b3f183e658dc749d and f417f44524e7fc098e787c718d838b32723c0b2d, targeting kernel versions up to and including 6.17.9 and 6.18. Users should update to a patched kernel version that includes these commits. Linux distribution maintainers (e.g., Red Hat, Ubuntu, SUSE) should be monitored for downstream advisory releases incorporating these fixes (kernel.org patch 1, kernel.org patch 2).