{"id":"CVE-2026-43067","title":"ext4: handle wraparound when searching for blocks for indirect mapped blocks","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\next4: handle wraparound when searching for blocks for indirect mapped blocks\n\nCommit 4865c768b563 (\"ext4: always allocate blocks only from groups\ninode can use\") restri…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 9d89b9d55e25cb340c5b4b769876edc551b7a9ff < f89bba144938921a2249237ad04a0183ff3f8930","Linux >= 1b0edd6022a3f44ce87fea9959a9310f4628fbea < 83170a05908b6cf2fb3235d3065bf613ff866f3c","Linux >= 9eea2f57d11b30049ff996ac3eff6e0dc8089e5f < 4bec4a498ce86314d470ae6144120461f2138c29","Linux >= 34c803edc0b3365a42efcf9815acab63b4cf54e0 < 12624c5b724a81e14e532972b40d863b0de3b7d1","Linux >= 321ed8d559c951e71ad2d2d69a4cf0445644e865 < 2a368ccddfc492a0aa951e2caef2985f20e96503","Linux >= 4865c768b563deff1b6a6384e74a62f143427b42 < bb81702370fad22c06ca12b6e1648754dbc37e0f","Linux 16fce6b6c0b247258c6c217fce5a48abf50f6964","Linux >= 5.15.203 < 5.16","Linux >= 6.1.167 < 6.1.168","Linux >= 6.6.130 < 6.6.134","Linux >= 6.12.77 < 6.12.80","Linux >= 6.18.14 < 6.18.21","Linux >= 6.19.4 < 6.19.11"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"total","timestamp":"2026-10-16T15:14:16.994971Z"},"published":"2026-05-05","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:20:31.250Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-43067","references":[{"url":"https://git.kernel.org/stable/c/f89bba144938921a2249237ad04a0183ff3f8930"},{"url":"https://git.kernel.org/stable/c/83170a05908b6cf2fb3235d3065bf613ff866f3c"},{"url":"https://git.kernel.org/stable/c/4bec4a498ce86314d470ae6144120461f2138c29"},{"url":"https://git.kernel.org/stable/c/12624c5b724a81e14e532972b40d863b0de3b7d1"},{"url":"https://git.kernel.org/stable/c/2a368ccddfc492a0aa951e2caef2985f20e96503"},{"url":"https://git.kernel.org/stable/c/bb81702370fad22c06ca12b6e1648754dbc37e0f"}],"tags":["cve.org"],"epss":0.00721,"epssPercentile":0.5301,"ingestedAt":"2026-10-16T17:24:46.680Z","slug":"CVE-2026-43067","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\next4: handle wraparound when searching for blocks for indirect mapped blocks\n\nCommit 4865c768b563 (\"ext4: always allocate blocks only from groups\ninode can use\") restricts what blocks will be allocated for indirect\nblock based files to block numbers that fit within 32-bit block\nnumbers.\n\nHowever, when using a review bot running on the latest Gemini LLM to\ncheck this commit when backporting into an LTS based kernel, it raised\nthis concern:\n\n   If ac->ac_g_ex.fe_group is >= ngroups (for instance, if the goal\n   group was populated via stream allocation from s_mb_last_groups),\n   then start will be >= ngroups.\n\n   Does this allow allocating blocks beyond the 32-bit limit for\n   indirect block mapped files? The commit message mentions that\n   ext4_mb_scan_groups_linear() takes care to not select unsupported\n   groups. However, its loop uses group = *start, and the very first\n   iteration will call ext4_mb_scan_group() with this unsupported\n   group because next_linear_group() is only called at the end of the\n   iteration.\n\nAfter reviewing the code paths involved and considering the LLM\nreview, I determined that this can happen when there is a file system\nwhere some files/directories are extent-mapped and others are\nindirect-block mapped.  To address this, add a safety clamp in\next4_mb_scan_groups().\n\n## Affected\n\n- `Linux >= 9d89b9d55e25cb340c5b4b769876edc551b7a9ff < f89bba144938921a2249237ad04a0183ff3f8930`\n- `Linux >= 1b0edd6022a3f44ce87fea9959a9310f4628fbea < 83170a05908b6cf2fb3235d3065bf613ff866f3c`\n- `Linux >= 9eea2f57d11b30049ff996ac3eff6e0dc8089e5f < 4bec4a498ce86314d470ae6144120461f2138c29`\n- `Linux >= 34c803edc0b3365a42efcf9815acab63b4cf54e0 < 12624c5b724a81e14e532972b40d863b0de3b7d1`\n- `Linux >= 321ed8d559c951e71ad2d2d69a4cf0445644e865 < 2a368ccddfc492a0aa951e2caef2985f20e96503`\n- `Linux >= 4865c768b563deff1b6a6384e74a62f143427b42 < bb81702370fad22c06ca12b6e1648754dbc37e0f`\n- `Linux 16fce6b6c0b247258c6c217fce5a48abf50f6964`\n- `Linux >= 5.15.203 < 5.16`\n- `Linux >= 6.1.167 < 6.1.168`\n- `Linux >= 6.6.130 < 6.6.134`\n- `Linux >= 6.12.77 < 6.12.80`\n- `Linux >= 6.18.14 < 6.18.21`\n- `Linux >= 6.19.4 < 6.19.11`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}