Linux KernelOperating system · Linux
CVE-2026-43067
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn the Linux kernel, the following vulnerability has been resolved: ext4: handle wraparound when searching for blocks for indirect mapped blocks Commit 4865c768b563 ("ext4: always allocate blocks only from groups inode can use") restricts what blocks will be allocated for indirect block based files to block numbers that fit within 32-bit block numbers. However, when using a review bot running on the latest Gemini LLM to check this commit when backporting into an LTS based kernel, it raised this concern: If ac->ac_g_ex.fe_group is >= ngroups (for instance, if the goal group was populated via stream allocation from s_mb_last_groups), then start will be >= ngroups. Does this allow allocating blocks beyond the 32-bit limit for indirect block mapped files? The commit message mentions that ext4_mb_scan_groups_linear() takes care to not select unsupported groups. However, its loop uses group = *start, and the very first iteration will call ext4_mb_scan_group() with this unsupported group because next_linear_group() is only called at the end of the iteration. After reviewing the code paths involved and considering the LLM review, I determined that this can happen when there is a file system where some files/directories are extent-mapped and others are indirect-block mapped. To address this, add a safety clamp in ext4_mb_scan_groups().
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA vulnerability in ext4's block allocation allows out-of-bounds group selection due to missing bounds checking. When searching for blocks via ext4_mb_scan_groups_linear(), if ac->ac_g_ex.fe_group >= ngroups (e.g., from stream allocation via s_mb_last_groups), the first iteration calls ext4_mb_scan_group() with an unsupported group because next_linear_group() is only called at loop end. This can cause allocation beyond the 32-bit limit for indirect block mapped files on filesystems with mixed extent/indirect-mapped files.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Linux KernelOperating system
>= 5.15.203, < 5.16>= 6.6.130, < 6.6.134>= 6.12.77, < 6.12.80>= 6.18.14, < 6.18.21>= 6.19.4, < 6.19.11= 6.1.167CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check kernel versionRun `uname -r` or `cat /proc/version` to get the running kernel versionAffected if The kernel version falls within any of these ranges: >= 5.15.203 and < 5.16; >= 6.6.130 and < 6.6.134; >= 6.12.77 and < 6.12.80; >= 6.18.14 and < 6.18.21; >= 6.19.4 and < 6.19.11; or equals exactly 6.1.167
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Identify ext4 filesystems in useRun `mount | grep ext4` or `df -T | grep ext4` to list mounted ext4 filesystemsAffected if Any ext4 filesystem is mounted and actively used for file storage
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Check for indirect-block mapped files on ext4Run `find /mountpoint -xattr -p 2>/dev/null` or inspect inodes using `debugfs -R 'stat <inode>' /dev/device` to see if files use indirect block mapping (no EXT4_EXTENTS_FLAG flag)Affected if Indirect-block mapped files exist on ext4 filesystems (files not using extent-based block mapping)
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Verify stream allocation usageInspect /proc/fs/ext4/*/mb_stats for s_mb_last_groups activity or monitor file operations that use sequential block allocation streamsAffected if Workloads perform stream-style allocations that utilize s_mb_last_groups on ext4
A system is affected if it runs a vulnerable kernel version AND has ext4 filesystems with indirect-block mapped files subject to stream allocation patterns.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped5.166.6.1346.12.80
Apply the kernel patch adding a safety clamp in ext4_mb_scan_groups() to bounds-check group values before block allocation proceeds. Prioritize patching on systems using indirect-block mapped files on ext4 filesystems.
Kernel version >= 5.16, >= 6.6.134, >= 6.12.80, or >= 6.18.21 depending on branch
- 1. Identify the current running Linux kernel version using `uname -r`
- 2. Determine which version branch the current kernel is on (5.15.x, 6.6.x, 6.12.x, or 6.18.x)
- 3. For 5.15.x branch: upgrade to kernel version 5.16 or later
- 4. For 6.6.x branch: upgrade to kernel version 6.6.134 or later
- 5. For 6.12.x branch: upgrade to kernel version 6.12.80 or later
- 6. For 6.18.x branch: upgrade to kernel version 6.18.21 or later
- 7. Alternatively, apply the vendor patch commit 12624c5b724a81e14e532972b40d863b0de3b7d1 to the currently running kernel
- 8. Reboot the system to apply the patched kernel
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Linux Kernel
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-43067 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-43067 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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