{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63817","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-07-19T07:54:57.014Z","datePublished":"2026-07-19T12:02:16.441Z","dateUpdated":"2026-08-17T04:51:24.577Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-17T04:51:24.577Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: validate compress cache inode only when enabled\n\nF2FS_COMPRESS_INO() uses NM_I(sbi)->max_nid as the synthetic inode\nnumber for the compressed page cache inode. That inode only exists when\nthe compress_cache mount option is enabled.\n\nWhen compress_cache is disabled, max_nid is outside the valid inode\nrange. A corrupted directory entry that points to ino == max_nid should\ntherefore be rejected by f2fs_check_nid_range(). However, is_meta_ino()\ncurrently treats F2FS_COMPRESS_INO() as a meta inode unconditionally,\nso f2fs_iget() bypasses do_read_inode() and its nid range check, and\ninstantiates a fake internal inode instead.\n\nGate the compressed cache inode case on COMPRESS_CACHE, matching\nf2fs_init_compress_inode(). With compress_cache disabled, ino ==\nmax_nid now follows the normal inode path and is rejected as an\nout-of-range nid."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is reached through local VFS operations (open/lookup, get_parent, mount-time recovery, and background GC) on a mounted F2FS filesystem; there is no direct network packet handler, though NFS export is a secondary path still requiring local filesystem access to plant corruption.\nAC:L - An attacker can deterministically craft an F2FS image with a directory entry pointing at ino=max_nid (known at image creation) and reliably trigger f2fs_iget() on mount or lookup without depending on uncontrollable runtime conditions.\nPR:L - Triggering requires mounting or writing to F2FS, which needs CAP_SYS_ADMIN but is obtainable by an unprivileged user via user namespaces; planting a corrupted dentry also requires only low-privilege write access to the filesystem.\nUI:N - Once a crafted or corrupted filesystem is in place, exploitation is driven entirely by attacker-initiated syscalls (mount, lookup, open) or automatic kernel paths (GC, recovery) with no victim interaction required.\nS:U - Impact is confined to kernel memory/filesystem integrity on the host running the affected F2FS code; it does not cross a VM, container, or IOMMU security boundary in the manner of a guest-to-host escape.\nC:H - Bypassing inode validation instantiates a mis-typed, uninitialized inode that subsequent f2fs data and node paths operate on, creating a type-confusion condition that can be leveraged for arbitrary kernel memory read primitives.\nI:H - The fake compress-cache inode is wired with compress address_space operations and skips normal inode teardown, enabling type confusion that can be abused for arbitrary kernel memory writes or control-flow hijacking.\nA:H - Operating on an invalid synthetic inode in GC, recovery, or lookup paths can trigger kernel oops, EFSCORRUPTED error handling, or filesystem panic (errors=panic), causing denial of service or system crash."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/f2fs/inode.c"],"versions":[{"version":"6ce19aff0b8cd386860855185c6cd79337fc4d2b","lessThan":"fcc051d377a9701a452e7663a1a8223c26225df9","status":"affected","versionType":"git"},{"version":"6ce19aff0b8cd386860855185c6cd79337fc4d2b","lessThan":"29115b8c9172d34e67ab26cc4f6c209b7a236d7a","status":"affected","versionType":"git"},{"version":"6ce19aff0b8cd386860855185c6cd79337fc4d2b","lessThan":"13e4b59d3a9413f66f116fa6c4828519b960a5ea","status":"affected","versionType":"git"},{"version":"6ce19aff0b8cd386860855185c6cd79337fc4d2b","lessThan":"16161444c30d8dff9428abbae42b72ce4e32a932","status":"affected","versionType":"git"},{"version":"6ce19aff0b8cd386860855185c6cd79337fc4d2b","lessThan":"77f216ff9ce5cde8eed9f6d12707e906dffdc9f7","status":"affected","versionType":"git"},{"version":"6ce19aff0b8cd386860855185c6cd79337fc4d2b","lessThan":"0969926d987bbde9a1aa49da317582ba37095805","status":"affected","versionType":"git"},{"version":"6ce19aff0b8cd386860855185c6cd79337fc4d2b","lessThan":"5073c66a96a9c23c0c2533ed4ed06e42f9021208","status":"affected","versionType":"git"},{"version":"a23706426da9b611be5beae0f3faa260fb453b4e","status":"affected","versionType":"git"},{"version":"5.13.19","lessThan":"5.14","status":"affected","versionType":"semver"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/f2fs/inode.c"],"versions":[{"version":"5.14","status":"affected"},{"version":"0","lessThan":"5.14","status":"unaffected","versionType":"semver"},{"version":"5.15.212","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.177","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.144","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.95","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.38","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.3","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","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":"5.14","versionEndExcluding":"5.15.212"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.1.177"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.6.144"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.12.95"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.18.38"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"7.1.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13.19"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/fcc051d377a9701a452e7663a1a8223c26225df9"},{"url":"https://git.kernel.org/stable/c/29115b8c9172d34e67ab26cc4f6c209b7a236d7a"},{"url":"https://git.kernel.org/stable/c/13e4b59d3a9413f66f116fa6c4828519b960a5ea"},{"url":"https://git.kernel.org/stable/c/16161444c30d8dff9428abbae42b72ce4e32a932"},{"url":"https://git.kernel.org/stable/c/77f216ff9ce5cde8eed9f6d12707e906dffdc9f7"},{"url":"https://git.kernel.org/stable/c/0969926d987bbde9a1aa49da317582ba37095805"},{"url":"https://git.kernel.org/stable/c/5073c66a96a9c23c0c2533ed4ed06e42f9021208"}],"title":"f2fs: validate compress cache inode only when enabled","x_generator":{"engine":"bippy-1.2.0"}}}}