{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-90203", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.792Z", "datePublished": "2026-09-17T16:07:20.180Z", "dateUpdated": "2026-10-19T08:59:39.333Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:59:39.333Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSquashfs: check block offset is not negative\n\nIf a negative offset is read off disk (for example the offset into the\ndecompressed fragment block), this will cause squashfs_copy_data() to\nperform an out of bounds access.\n\nFix by checking if offset is negative, and returning 0. This matches\nexisting behaviour where an offset beyond the block returns 0 bytes\ncopied.\n\nTo trigger this out of bounds access requires a crafted Squashfs\nfilesystem and CAP_SYS_ADMIN to mount it. Unprivileged users will not be\nable to mount such a filesystem, but once mounted, an unprivileged user\ncan trigger the out of bounds access by reading the crafted file with the\nnegative offset." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H", "baseScore": 7.1, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The bad bytes are squashfs_reg_inode.offset/squashfs_lreg_inode.offset, stored by squashfs_read_inode() as fragment_offset and used by squashfs_read_folio()/squashfs_readahead_fragment() → squashfs_copy_data() on a loop/block-backed image. That field is on-disk fragment metadata, not a network protocol message; squashfs_fs_type is FS_REQUIRES_DEV.\nAC:L - squashfs_read_inode() assigns le32_to_cpu(sqsh_ino->offset) to signed int fragment_offset with no range check, so a high-bit-set on-disk value is negative. read() of that file's tail (generic_file_read_iter → squashfs_read_folio) then calls squashfs_copy_data() with that offset; there is no race.\nPR:N - squashfs_fs_type has no FS_USERNS_MOUNT, so mount_capable() needs init-namespace CAP_SYS_ADMIN, but the attacker who crafts the image needs no account. After that privileged mount, an unprivileged read of the crafted file is enough; the mount is scored as User Interaction, not Privileges Required.\nUI:R - The negative fragment_offset exists only in an attacker-supplied Squashfs image, and squashfs_copy_data() runs only after that image is mounted and the crafted file is read. The mount is the required victim action; a standing snapd or live-image setup does not remove it.\nS:U - squashfs_copy_data() indexes the fragment cache's kmalloc'd data[] array and memcpy's into the file's own page-cache folio in the same kernel. This is not a KVM/Xen guest-to-host escape or an IOMMU/DMA bypass.\nC:H - A negative offset makes squashfs_copy_data() evaluate entry->data[offset/PAGE_SIZE] before the kcalloc'd pointer array, then memcpy up to PAGE_SIZE bytes from that address into the folio returned by read(). That is an unbounded OOB kernel read into userspace, not a few-byte leak.\nI:N - The memcpy destination is the kmap of the crafted file's own folio in squashfs_fill_page()/squashfs_readahead_fragment(); the source is the OOB pointer. Length is capped by avail (≤PAGE_SIZE), so this path does not write kernel objects out of bounds.\nA:H - Indexing entry->data[] with a negative offset/PAGE_SIZE and memcpy from the resulting pointer is the same squashfs_copy_data() out-of-bounds access that produced a general protection fault in CVE-2026-23388; an unmapped address oopses the kernel." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/squashfs/cache.c" ], "versions": [ { "version": "f400e12656ab518be107febfe2315fb1eab5a342", "lessThan": "b169185d5c672b989985c6c2e38cafab2548ba88", "status": "affected", "versionType": "git" }, { "version": "f400e12656ab518be107febfe2315fb1eab5a342", "lessThan": "c2a126fca820ae74872da28de68dc74d4595dc4b", "status": "affected", "versionType": "git" }, { "version": "f400e12656ab518be107febfe2315fb1eab5a342", "lessThan": "95dadf366c117dcdca78a570e6832071deab1ecd", "status": "affected", "versionType": "git" }, { "version": "f400e12656ab518be107febfe2315fb1eab5a342", "lessThan": "3d2f0cb66c909ea2312cdef465165bb9a3ba2d84", "status": "affected", "versionType": "git" }, { "version": "f400e12656ab518be107febfe2315fb1eab5a342", "lessThan": "bbb2218eb072b0a15dc063929200183bd23c2344", "status": "affected", "versionType": "git" }, { "version": "f400e12656ab518be107febfe2315fb1eab5a342", "lessThan": "d0a3729d464fcf516416a41cf304c0c92126ee03", "status": "affected", "versionType": "git" }, { "version": "f400e12656ab518be107febfe2315fb1eab5a342", "lessThan": "e4afd90bc7bf3dd477970c6c42bdd29ad3fda7fe", "status": "affected", "versionType": "git" }, { "version": "f400e12656ab518be107febfe2315fb1eab5a342", "lessThan": "e300eb5002925b29be803d2661af07266cfa267e", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/squashfs/cache.c" ], "versions": [ { "version": "2.6.29", "status": "affected" }, { "version": "0", "lessThan": "2.6.29", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.270", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.221", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.188", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.157", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.110", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.52", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.6", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.29", "versionEndExcluding": "5.10.270" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.29", "versionEndExcluding": "5.15.221" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.29", "versionEndExcluding": "6.1.188" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.29", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.29", "versionEndExcluding": "6.12.110" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.29", "versionEndExcluding": "6.18.52" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.29", "versionEndExcluding": "7.2.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.29", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/b169185d5c672b989985c6c2e38cafab2548ba88" }, { "url": "https://git.kernel.org/stable/c/c2a126fca820ae74872da28de68dc74d4595dc4b" }, { "url": "https://git.kernel.org/stable/c/95dadf366c117dcdca78a570e6832071deab1ecd" }, { "url": "https://git.kernel.org/stable/c/3d2f0cb66c909ea2312cdef465165bb9a3ba2d84" }, { "url": "https://git.kernel.org/stable/c/bbb2218eb072b0a15dc063929200183bd23c2344" }, { "url": "https://git.kernel.org/stable/c/d0a3729d464fcf516416a41cf304c0c92126ee03" }, { "url": "https://git.kernel.org/stable/c/e4afd90bc7bf3dd477970c6c42bdd29ad3fda7fe" }, { "url": "https://git.kernel.org/stable/c/e300eb5002925b29be803d2661af07266cfa267e" } ], "title": "Squashfs: check block offset is not negative", "x_generator": { "engine": "bippy-1.2.0" } } } }