CVE-2026-43046
Heap Buffer Overflow in Btrfs Filesystem
Publication date: 2026-05-01
Last updated on: 2026-05-01
Assigner: kernel.org
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | kernel | 7.0.0-rc2-next-20260310 |
| linux | linux_kernel | 7.0.0-rc2-next-20260310 |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in the Linux kernel's btrfs filesystem. It involves improper validation of certain metadata fields called drop_progress and drop_level in root items during mount time relocation recovery.
Specifically, when recovering relocation at mount time, the kernel expects that if drop_progress.objectid is non-zero (indicating an interrupted snapshot drop operation), then drop_level must also be non-zero. However, this invariant was not validated when reading root items from disk, allowing corrupted metadata with drop_progress.objectid != 0 and drop_level == 0 to exist.
This invalid state triggers a kernel BUG (crash) in functions merge_reloc_root() and btrfs_drop_snapshot() because they use BUG_ON(level == 0) to guard against this impossible state.
The fix involves adding validation in the tree-checker to reject such malformed metadata before it causes a kernel crash.
How can this vulnerability impact me? :
This vulnerability can cause the Linux kernel to crash (kernel BUG) during the mount process of a btrfs filesystem if corrupted metadata is present.
Such crashes can lead to system instability, potential data loss, or denial of service because the filesystem cannot be mounted properly.
The issue arises from corrupted or malformed on-disk metadata that violates expected invariants, which could be triggered unintentionally by disk corruption or potentially by an attacker who can manipulate the filesystem metadata.
What immediate steps should I take to mitigate this vulnerability?
The vulnerability is fixed by validating the root_item invariant in the tree-checker when reading root items from disk. Specifically, if drop_progress.objectid is non-zero, drop_level must also be non-zero. Malformed metadata with a non-zero drop_progress.objectid and zero drop_level is rejected with -EUCLEAN before it can trigger the kernel BUG_ON conditions.
Therefore, the immediate mitigation step is to update the Linux kernel to a version that includes this fix, which ensures corrupted btrfs metadata is detected and rejected early, preventing the BUG_ON crash.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
The provided information about the vulnerability CVE-2026-43046 does not include any details regarding its impact on compliance with common standards and regulations such as GDPR or HIPAA.
How can this vulnerability be detected on my network or system? Can you suggest some commands?
This vulnerability manifests as a kernel BUG triggered by invalid btrfs metadata during mount time, specifically when recovering relocation. Detection involves monitoring for kernel BUG messages related to btrfs, such as those containing 'kernel BUG at fs/btrfs/relocation.c:1545' or 'BUG_ON(level == 0)'.
You can check your system logs (e.g., using dmesg or journalctl) for such kernel BUG messages indicating this issue.
- dmesg | grep -i 'btrfs.*BUG_ON'
- journalctl -k | grep -i 'btrfs.*BUG_ON'
Additionally, since the issue relates to corrupted btrfs root items with invalid drop_progress and drop_level fields, running btrfs filesystem checks or tree-checker tools that validate root items could help detect malformed metadata before mount.
However, no specific commands or tools are provided in the available information to directly detect this vulnerability beyond monitoring for kernel BUG messages during mount or filesystem operations.