{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-43067", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-05-01T14:12:55.981Z", "datePublished": "2026-05-05T15:23:26.717Z", "dateUpdated": "2026-08-05T12:25:42.475Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:25:42.475Z" }, "descriptions": [ { "lang": "en", "value": "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\") 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()." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - In a reasonable high-impact deployment, a writable ext4 filesystem can be exported by in-kernel NFS or ksmbd, whose WRITE handlers enter the same VFS/ext4 allocation path. Local writes also reach it, but network is the highest defensible vector for an exported writable share.\nAC:L - Once the affected large mixed-format ext4 filesystem state exists, triggering is a normal file allocation/write path with no race or probabilistic memory condition. The attacker can drive stream allocation and indirect-file allocation through repeated writes.\nPR:N - A writable anonymous or guest NFS/SMB export can reach the vulnerable write path without local credentials or kernel capabilities. Even locally, only ordinary write permission to an affected file is needed, not administrative privilege.\nUI:N - No victim action is required after the vulnerable filesystem/share is available. The attacker triggers allocation directly by writing data.\nS:U - The impact remains within the kernel/filesystem security authority. This is not a VM escape, IOMMU bypass, or cross-authority sandbox escape.\nC:H - The bug can allocate a physical block above the 32-bit indirect-block limit and then store it through a 32-bit indirect pointer, wrapping the file mapping to another on-disk block. That can expose arbitrary file data from the same filesystem through the attacker's file.\nI:H - The wrapped indirect pointer can make attacker writes target blocks that were not actually allocated to the file. This can overwrite other file data or corrupt the filesystem.\nA:H - Filesystem corruption can make data unavailable and can force ext4 errors or read-only/remediation states. Repeated writes can reliably recreate the corruption on an affected deployment." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/ext4/mballoc.c" ], "versions": [ { "version": "9d89b9d55e25cb340c5b4b769876edc551b7a9ff", "lessThan": "f89bba144938921a2249237ad04a0183ff3f8930", "status": "affected", "versionType": "git" }, { "version": "1b0edd6022a3f44ce87fea9959a9310f4628fbea", "lessThan": "83170a05908b6cf2fb3235d3065bf613ff866f3c", "status": "affected", "versionType": "git" }, { "version": "9eea2f57d11b30049ff996ac3eff6e0dc8089e5f", "lessThan": "4bec4a498ce86314d470ae6144120461f2138c29", "status": "affected", "versionType": "git" }, { "version": "34c803edc0b3365a42efcf9815acab63b4cf54e0", "lessThan": "12624c5b724a81e14e532972b40d863b0de3b7d1", "status": "affected", "versionType": "git" }, { "version": "321ed8d559c951e71ad2d2d69a4cf0445644e865", "lessThan": "2a368ccddfc492a0aa951e2caef2985f20e96503", "status": "affected", "versionType": "git" }, { "version": "4865c768b563deff1b6a6384e74a62f143427b42", "lessThan": "bb81702370fad22c06ca12b6e1648754dbc37e0f", "status": "affected", "versionType": "git" }, { "version": "16fce6b6c0b247258c6c217fce5a48abf50f6964", "status": "affected", "versionType": "git" }, { "version": "5.15.203", "lessThan": "5.16", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/ext4/mballoc.c" ], "versions": [ { "version": "6.1.167", "lessThan": "6.1.168", "status": "affected", "versionType": "semver" }, { "version": "6.6.130", "lessThan": "6.6.134", "status": "affected", "versionType": "semver" }, { "version": "6.12.77", "lessThan": "6.12.80", "status": "affected", "versionType": "semver" }, { "version": "6.18.14", "lessThan": "6.18.21", "status": "affected", "versionType": "semver" }, { "version": "6.19.4", "lessThan": "6.19.11", "status": "affected", "versionType": "semver" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.167", "versionEndExcluding": "6.1.168" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.130", "versionEndExcluding": "6.6.134" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.77", "versionEndExcluding": "6.12.80" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18.14", "versionEndExcluding": "6.18.21" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19.4", "versionEndExcluding": "6.19.11" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.203" } ] } ] } ], "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" } ], "title": "ext4: handle wraparound when searching for blocks for indirect mapped blocks", "x_generator": { "engine": "bippy-1.2.0" } } } }