{"api_version":"1","generated_at":"2026-09-05T08:47:46+00:00","cve":"CVE-2026-63818","urls":{"html":"https://cve.report/CVE-2026-63818","api":"https://cve.report/api/cve/CVE-2026-63818.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-63818","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63818"},"summary":{"title":"f2fs: validate orphan inode entry count","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: validate orphan inode entry count\n\nf2fs_recover_orphan_inodes() trusts the orphan block entry_count when\nreplaying orphan inodes from the checkpoint pack. A corrupted entry_count\nlarger than F2FS_ORPHANS_PER_BLOCK makes the recovery loop read past the\nino[] array and interpret footer or following data as inode numbers.\n\nOn a crafted image, mounting an unpatched kernel can drive orphan recovery\ninto f2fs_bug_on() and panic the kernel. Validate entry_count before\nconsuming entries so corrupted checkpoint data fails the mount with\n-EFSCORRUPTED and requests fsck instead.\n\nSet ERROR_INCONSISTENT_ORPHAN as well, so the corruption reason can be\nrecorded in the superblock s_errors[] field. This gives fsck a persistent\nhint even though mount-time orphan recovery failure may leave no chance to\npersist SBI_NEED_FSCK through a checkpoint.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-07-19 12:16:54","updated_at":"2026-08-17 05:17:19"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"8.4","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.4,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"8.4","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"baseScore":8.4,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/846c499a65816d13f1186e3090e825e8bb8bcb8b","name":"https://git.kernel.org/stable/c/846c499a65816d13f1186e3090e825e8bb8bcb8b","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/550511a2470f6d204fa07b331f048bd2d3c51280","name":"https://git.kernel.org/stable/c/550511a2470f6d204fa07b331f048bd2d3c51280","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/210c210c92d78fdf5051bc55c5c69044b1a2150a","name":"https://git.kernel.org/stable/c/210c210c92d78fdf5051bc55c5c69044b1a2150a","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d2f236196d542ccd8505736e41c3a1d3f0305f6f","name":"https://git.kernel.org/stable/c/d2f236196d542ccd8505736e41c3a1d3f0305f6f","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/8aad54746c251f2c2370118df766c0c82e2d2091","name":"https://git.kernel.org/stable/c/8aad54746c251f2c2370118df766c0c82e2d2091","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ad101d15716f5a24d1fa82a849f80430c805a3dd","name":"https://git.kernel.org/stable/c/ad101d15716f5a24d1fa82a849f80430c805a3dd","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/2e12381d4495dc8b0ff042c6856022b2e359835c","name":"https://git.kernel.org/stable/c/2e12381d4495dc8b0ff042c6856022b2e359835c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d18c81f5d0ecd5796aa47d66d98f2dd54d8d0f70","name":"https://git.kernel.org/stable/c/d18c81f5d0ecd5796aa47d66d98f2dd54d8d0f70","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63818","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63818","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 127e670abfa7fa150f6550d620ded930f5bdb4e7 210c210c92d78fdf5051bc55c5c69044b1a2150a git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 127e670abfa7fa150f6550d620ded930f5bdb4e7 ad101d15716f5a24d1fa82a849f80430c805a3dd git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 127e670abfa7fa150f6550d620ded930f5bdb4e7 d18c81f5d0ecd5796aa47d66d98f2dd54d8d0f70 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 127e670abfa7fa150f6550d620ded930f5bdb4e7 d2f236196d542ccd8505736e41c3a1d3f0305f6f git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.212 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.178 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.145 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.96 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.38 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1.3 7.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"63818","cve":"CVE-2026-63818","epss":"0.001320000","percentile":"0.031980000","score_date":"2026-07-29","updated_at":"2026-07-30 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the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: validate orphan inode entry count\n\nf2fs_recover_orphan_inodes() trusts the orphan block entry_count when\nreplaying orphan inodes from the checkpoint pack. A corrupted entry_count\nlarger than F2FS_ORPHANS_PER_BLOCK makes the recovery loop read past the\nino[] array and interpret footer or following data as inode numbers.\n\nOn a crafted image, mounting an unpatched kernel can drive orphan recovery\ninto f2fs_bug_on() and panic the kernel. Validate entry_count before\nconsuming entries so corrupted checkpoint data fails the mount with\n-EFSCORRUPTED and requests fsck instead.\n\nSet ERROR_INCONSISTENT_ORPHAN as well, so the corruption reason can be\nrecorded in the superblock s_errors[] field. This gives fsck a persistent\nhint even though mount-time orphan recovery failure may leave no chance to\npersist SBI_NEED_FSCK through a checkpoint."}],"metrics":[{"cvssV3_1":{"baseScore":8.4,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable code runs only during F2FS mount via the mount syscall path (fs_context → get_tree_bdev → f2fs_fill_super → f2fs_recover_orphan_inodes); it is not reachable from network protocols or device drivers.\nAC:L - An attacker fully controls the crafted on-disk orphan block including entry_count and ino[] contents, so triggering the bug is reliable once a victim or privileged auto-mount path mounts the image; no race or rare layout dependency is required.\nPR:N - The attacker needs no privileges on the victim system—only a malicious F2FS image delivered via removable media, downloaded disk image, or similar that a privileged mount/auto-mount daemon later processes.\nUI:N - No victim interaction is required when the attacker mounts their own crafted image (e.g., loop mount in a user namespace with CAP_SYS_ADMIN), and automated privileged mount paths can process attacker-supplied media without further user action.\nS:U - Impact is confined to kernel/filesystem integrity and availability on the host mounting the image; it does not cross a VM, container, or IOMMU security boundary.\nC:H - The unchecked loop indexes past ino[F2FS_ORPHANS_PER_BLOCK-1] into the block footer and beyond the 4 KiB orphan block, constituting an out-of-bounds read of attacker-influenced metadata that can leak kernel-adjacent memory contents.\nI:H - Misinterpreted inode numbers are passed to recover_orphan_inode(), which clear_nlink() and iput() (truncating data) on matching real inodes, enabling deliberate destruction of filesystem contents from a crafted image.\nA:H - Crafted entry_count values drive f2fs_bug_on() on -ENOENT (kernel BUG/panic with CONFIG_F2FS_CHECK_FS, or WARN/oops otherwise) and can hang or crash the system during mount via unbounded orphan recovery iteration."}]}],"providerMetadata":{"dateUpdated":"2026-08-17T04:51:25.680Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/210c210c92d78fdf5051bc55c5c69044b1a2150a"},{"url":"https://git.kernel.org/stable/c/ad101d15716f5a24d1fa82a849f80430c805a3dd"},{"url":"https://git.kernel.org/stable/c/d18c81f5d0ecd5796aa47d66d98f2dd54d8d0f70"},{"url":"https://git.kernel.org/stable/c/d2f236196d542ccd8505736e41c3a1d3f0305f6f"},{"url":"https://git.kernel.org/stable/c/550511a2470f6d204fa07b331f048bd2d3c51280"},{"url":"https://git.kernel.org/stable/c/8aad54746c251f2c2370118df766c0c82e2d2091"},{"url":"https://git.kernel.org/stable/c/2e12381d4495dc8b0ff042c6856022b2e359835c"},{"url":"https://git.kernel.org/stable/c/846c499a65816d13f1186e3090e825e8bb8bcb8b"}],"title":"f2fs: validate orphan inode entry count","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-63818","datePublished":"2026-07-19T12:02:17.022Z","dateReserved":"2026-07-19T07:54:57.014Z","dateUpdated":"2026-08-17T04:51:25.680Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-19 12:16:54","lastModifiedDate":"2026-08-17 05:17:19","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.4,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":2.5,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"63818","Ordinal":"1","Title":"f2fs: validate orphan inode entry count","CVE":"CVE-2026-63818","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"63818","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: validate orphan inode entry count\n\nf2fs_recover_orphan_inodes() trusts the orphan block entry_count when\nreplaying orphan inodes from the checkpoint pack. A corrupted entry_count\nlarger than F2FS_ORPHANS_PER_BLOCK makes the recovery loop read past the\nino[] array and interpret footer or following data as inode numbers.\n\nOn a crafted image, mounting an unpatched kernel can drive orphan recovery\ninto f2fs_bug_on() and panic the kernel. Validate entry_count before\nconsuming entries so corrupted checkpoint data fails the mount with\n-EFSCORRUPTED and requests fsck instead.\n\nSet ERROR_INCONSISTENT_ORPHAN as well, so the corruption reason can be\nrecorded in the superblock s_errors[] field. This gives fsck a persistent\nhint even though mount-time orphan recovery failure may leave no chance to\npersist SBI_NEED_FSCK through a checkpoint.","Type":"Description","Title":"f2fs: validate orphan inode entry count"}]}}}