CVE-2026-63818 (GCVE-0-2026-63818)
Vulnerability from cvelistv5
Published
2026-07-19 12:02
Modified
2026-08-17 04:51
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
f2fs: validate orphan inode entry count
f2fs_recover_orphan_inodes() trusts the orphan block entry_count when
replaying orphan inodes from the checkpoint pack. A corrupted entry_count
larger than F2FS_ORPHANS_PER_BLOCK makes the recovery loop read past the
ino[] array and interpret footer or following data as inode numbers.
On a crafted image, mounting an unpatched kernel can drive orphan recovery
into f2fs_bug_on() and panic the kernel. Validate entry_count before
consuming entries so corrupted checkpoint data fails the mount with
-EFSCORRUPTED and requests fsck instead.
Set ERROR_INCONSISTENT_ORPHAN as well, so the corruption reason can be
recorded in the superblock s_errors[] field. This gives fsck a persistent
hint even though mount-time orphan recovery failure may leave no chance to
persist SBI_NEED_FSCK through a checkpoint.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 127e670abfa7fa150f6550d620ded930f5bdb4e7 Version: 127e670abfa7fa150f6550d620ded930f5bdb4e7 Version: 127e670abfa7fa150f6550d620ded930f5bdb4e7 Version: 127e670abfa7fa150f6550d620ded930f5bdb4e7 Version: 127e670abfa7fa150f6550d620ded930f5bdb4e7 Version: 127e670abfa7fa150f6550d620ded930f5bdb4e7 Version: 127e670abfa7fa150f6550d620ded930f5bdb4e7 Version: 127e670abfa7fa150f6550d620ded930f5bdb4e7 |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/f2fs/checkpoint.c",
"include/linux/f2fs_fs.h"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
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"status": "affected",
"version": "127e670abfa7fa150f6550d620ded930f5bdb4e7",
"versionType": "git"
},
{
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"status": "affected",
"version": "127e670abfa7fa150f6550d620ded930f5bdb4e7",
"versionType": "git"
},
{
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"status": "affected",
"version": "127e670abfa7fa150f6550d620ded930f5bdb4e7",
"versionType": "git"
},
{
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"versionType": "git"
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{
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]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
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"include/linux/f2fs_fs.h"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "3.8"
},
{
"lessThan": "3.8",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.261",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.212",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.178",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.145",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.96",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.38",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.3",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.261",
"versionStartIncluding": "3.8",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.15.212",
"versionStartIncluding": "3.8",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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{
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.96",
"versionStartIncluding": "3.8",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.38",
"versionStartIncluding": "3.8",
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "3.8",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "3.8",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"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 \u2192 get_tree_bdev \u2192 f2fs_fill_super \u2192 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\u2014only 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"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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