{"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":"2026-09-18T17:53:41.435Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-18T17:53:41.435Z"},"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-rc1","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-rc1"}]}]}],"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"}}}}