CVE-2025-40209 Affecting kernel-docs-html package, versions <6.12.0-160000.9.1


Severity

Recommended
0.0
medium
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.03% (7th percentile)

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  • Snyk IDSNYK-SLES1600-KERNELDOCSHTML-15238911
  • published6 Feb 2026
  • disclosed2 Feb 2026

Introduced: 2 Feb 2026

CVE-2025-40209  (opens in a new tab)

How to fix?

Upgrade SLES:16.0.0 kernel-docs-html to version 6.12.0-160000.9.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-docs-html package and not the kernel-docs-html package as distributed by SLES. See How to fix? for SLES:16.0.0 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix memory leak of qgroup_list in btrfs_add_qgroup_relation

When btrfs_add_qgroup_relation() is called with invalid qgroup levels (src >= dst), the function returns -EINVAL directly without freeing the preallocated qgroup_list structure passed by the caller. This causes a memory leak because the caller unconditionally sets the pointer to NULL after the call, preventing any cleanup.

The issue occurs because the level validation check happens before the mutex is acquired and before any error handling path that would free the prealloc pointer. On this early return, the cleanup code at the 'out' label (which includes kfree(prealloc)) is never reached.

In btrfs_ioctl_qgroup_assign(), the code pattern is:

prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL);
ret = btrfs_add_qgroup_relation(trans, sa-&gt;src, sa-&gt;dst, prealloc);
prealloc = NULL;  // Always set to NULL regardless of return value
...
kfree(prealloc);  // This becomes kfree(NULL), does nothing

When the level check fails, 'prealloc' is never freed by either the callee or the caller, resulting in a 64-byte memory leak per failed operation. This can be triggered repeatedly by an unprivileged user with access to a writable btrfs mount, potentially exhausting kernel memory.

Fix this by freeing prealloc before the early return, ensuring prealloc is always freed on all error paths.

CVSS Base Scores

version 3.1