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The CVE-2025-39830 vulnerability is a memory leak in the Linux kernel’s mlx5 hardware steering (HWS) module. It occurs in the `hws_pool_buddy_init()` function responsible for initializing a buddy allocator for memory pooling. During initialization, if an error arises—such as a failed memory allocation for internal structures—the code enters an error cleanup path. This path calls cleanup routines to free some resources but omits deallocating the main allocator structure itself. Specifically, the `kfree()` function is missing for the `struct buddy_allocator` object allocated earlier. Consequently, each time initialization fails, the kernel memory allocated for this structure is not reclaimed, leading to a persistent leak. Repeated triggering of this error path, possibly through module loading failures or simulated allocation errors, can cumulatively exhaust available kernel memory. This may result in denial of service, system instability, or crashes due to memory exhaustion. The fix involves adding the missing `kfree()` call in the error path to ensure complete resource release.
DailyCVE form:
Platform: Linux kernel
Version: Multiple kernel versions
Vulnerability: Memory leak
Severity: Medium
date: 2025-09-16
Prediction: Patch released 2025-09-16
What Undercode Say:
Showing bash commands and codes related to the blog
Bash commands:
uname -r lsmod | grep mlx5 dmesg | grep hws
Code snippet:
// Vulnerable error path
if (error) {
cleanup_buddy_allocator(alloc);
// Missing kfree(alloc);
return error;
}
// Fixed version
if (error) {
cleanup_buddy_allocator(alloc);
kfree(alloc);
return error;
}
how Exploit:
Repeatedly trigger error path via module operations causing initialization failures to leak kernel memory leading to denial of service.
Protection from this CVE
Update Linux kernel, apply security patches, disable mlx5 HWS.
Impact:
Denial of service, memory exhaustion, system instability or crashes.
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Sources:
Reported By: nvd.nist.gov
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