CVE-2026-43067
Linux Kernel vulnerability
- Published5 May 2026
Description
In 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().
CVSS 3.1 breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HAffected products
Remediation
- https://git.kernel.org/stable/c/12624c5b724a81e14e532972b40d863b0de3b7d1
- https://git.kernel.org/stable/c/2a368ccddfc492a0aa951e2caef2985f20e96503
- https://git.kernel.org/stable/c/4bec4a498ce86314d470ae6144120461f2138c29
- https://git.kernel.org/stable/c/83170a05908b6cf2fb3235d3065bf613ff866f3c
- https://git.kernel.org/stable/c/bb81702370fad22c06ca12b6e1648754dbc37e0f
- https://git.kernel.org/stable/c/f89bba144938921a2249237ad04a0183ff3f8930
References
- https://git.kernel.org/stable/c/12624c5b724a81e14e532972b40d863b0de3b7d1
- https://git.kernel.org/stable/c/2a368ccddfc492a0aa951e2caef2985f20e96503
- https://git.kernel.org/stable/c/4bec4a498ce86314d470ae6144120461f2138c29
- https://git.kernel.org/stable/c/83170a05908b6cf2fb3235d3065bf613ff866f3c
- https://git.kernel.org/stable/c/bb81702370fad22c06ca12b6e1648754dbc37e0f
- https://git.kernel.org/stable/c/f89bba144938921a2249237ad04a0183ff3f8930
Frequently asked
Is CVE-2026-43067 being actively exploited?
CVE-2026-43067 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.72%.
How severe is CVE-2026-43067?
CVE-2026-43067 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.72% probability of exploitation.
Which products are affected by CVE-2026-43067?
Affected products include Linux Kernel.
How do I fix CVE-2026-43067?
Upgrade affected software to a fixed version, for example Linux Kernel 5.16 or later, then confirm no affected versions remain in your inventory.
How Secuno handles this
Secuno correlates vulnerabilities like CVE-2026-43067 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.
Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.