CVE-2025-39776: 
Linux Kernel vulnerability analysis and mitigation

In the Linux kernel, a vulnerability has been identified in the mm/debugvmpgtable component where page table entries are not properly cleared at destroyargs(). The issue was discovered in the debugvmpagetable test which allocates manual page table entries and mmstruct for testing purposes (Debian Security).

The vulnerability occurs when the debugvmpagetable test fails to clear page table entries with the *clear functions during destroyargs(). This leaves stale entries that can be problematic if another process allocates an mmstruct at the same address, potentially encountering the stale entry. This issue specifically manifests in debug kernels with CONFIGDEBUGVMPGTABLE=y enabled (Debian Security).

When exploited, this vulnerability can lead to incorrect page table entries being accessed by processes that subsequently allocate an mm_struct at the same address as a previously destroyed one, potentially causing memory corruption or system instability (Debian Security).

The issue has been fixed in Linux kernel version 6.16.5-1 for the unstable distribution and backported to various other versions. Some distributions like Bullseye are not affected as they don't contain the vulnerable code (Debian Security).