CVE-2026-43067ext4: handle wraparound when searching for blocks for indirect mapped blocks
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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
- 9.8 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Analyzed
- Record last updated
- Oct 16, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from 9d89b9d55e25cb340c5b4b769876edc551b7a9ff before f89bba144938921a2249237ad04a0183ff3f8930; from 1b0edd6022a3f44ce87fea9959a9310f4628fbea before 83170a05908b6cf2fb3235d3065bf613ff866f3c; 9eea2f57d11b30049ff996ac3eff6e0dc8089e5f builds before 4bec4a498ce86314d470ae6144120461f2138c29; from 34c803edc0b3365a42efcf9815acab63b4cf54e0 before 12624c5b724a81e14e532972b40d863b0de3b7d1; 321ed8d559c951e71ad2d2d69a4cf0445644e865 builds before 2a368ccddfc492a0aa951e2caef2985f20e96503; from 4865c768b563deff1b6a6384e74a62f143427b42 before bb81702370fad22c06ca12b6e1648754dbc37e0f; 16fce6b6c0b247258c6c217fce5a48abf50f6964; from 5.15.203 before 5.16 | CNA record |
linux linux_kernel linux:linux_kernel | from 5.15.203 before 5.16; from 6.6.130 before 6.6.134; from 6.12.77 before 6.12.80; from 6.18.14 before 6.18.21; from 6.19.4 before 6.19.11; 6.1.167 | NVD |
References
- https://git.kernel.org/stable/c/f89bba144938921a2249237ad04a0183ff3f8930patch
- https://git.kernel.org/stable/c/83170a05908b6cf2fb3235d3065bf613ff866f3cpatch
- https://git.kernel.org/stable/c/4bec4a498ce86314d470ae6144120461f2138c29patch
- https://git.kernel.org/stable/c/12624c5b724a81e14e532972b40d863b0de3b7d1patch
- https://git.kernel.org/stable/c/2a368ccddfc492a0aa951e2caef2985f20e96503patch
- https://git.kernel.org/stable/c/bb81702370fad22c06ca12b6e1648754dbc37e0fpatch
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.