CVE-2026-68442 (GCVE-0-2026-68442)
Vulnerability from cvelistv5
Published
2026-08-12 00:07
Modified
2026-08-17 05:05
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
btrfs: don't propagate EXTENT_FLAG_LOGGING to split extent maps
When btrfs_drop_extent_map_range() splits an extent map, the new split
maps inherit the original map's flags through a local 'flags' variable.
Commit f86f7a75e2fb ("btrfs: use the flags of an extent map to identify
the compression type") changed the EXTENT_FLAG_LOGGING clearing to
operate on em->flags instead of that local 'flags' copy, so a split of
an extent map that is currently being logged wrongly inherits
EXTENT_FLAG_LOGGING.
The flag is then never cleared on the split, and when it is freed while
still on the inode's modified_extents list (for example by the extent
map shrinker) it trips the WARN_ON(!list_empty(&em->list)) in
btrfs_free_extent_map() and leads to a use-after-free.
Clear EXTENT_FLAG_LOGGING from the local 'flags' copy used for the
splits and only clear EXTENT_FLAG_PINNED from em->flags, restoring the
behaviour prior to f86f7a75e2fb.
References
| URL | Tags | |
|---|---|---|
Impacted products
{
"containers": {
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"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/btrfs/extent_map.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
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"version": "f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9",
"versionType": "git"
},
{
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"version": "f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9",
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{
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"product": "Linux",
"programFiles": [
"fs/btrfs/extent_map.c"
],
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"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "6.8"
},
{
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"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.101",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.42",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.6",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
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"versionEndExcluding": "6.12.101",
"versionStartIncluding": "6.8",
"vulnerable": true
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{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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{
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}
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"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: don\u0027t propagate EXTENT_FLAG_LOGGING to split extent maps\n\nWhen btrfs_drop_extent_map_range() splits an extent map, the new split\nmaps inherit the original map\u0027s flags through a local \u0027flags\u0027 variable.\nCommit f86f7a75e2fb (\"btrfs: use the flags of an extent map to identify\nthe compression type\") changed the EXTENT_FLAG_LOGGING clearing to\noperate on em-\u003eflags instead of that local \u0027flags\u0027 copy, so a split of\nan extent map that is currently being logged wrongly inherits\nEXTENT_FLAG_LOGGING.\n\nThe flag is then never cleared on the split, and when it is freed while\nstill on the inode\u0027s modified_extents list (for example by the extent\nmap shrinker) it trips the WARN_ON(!list_empty(\u0026em-\u003elist)) in\nbtrfs_free_extent_map() and leads to a use-after-free.\n\nClear EXTENT_FLAG_LOGGING from the local \u0027flags\u0027 copy used for the\nsplits and only clear EXTENT_FLAG_PINNED from em-\u003eflags, restoring the\nbehaviour prior to f86f7a75e2fb."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The bug is in the btrfs in-memory extent map code, reached only through local file operations (write/writeback, fallocate punch hole, truncate, clone, fsync) on a btrfs filesystem; no remote protocol data is involved.\nAC:L - Although the flag is only mis-propagated while an fsync has an extent map flagged for logging, the attacker controls both sides of the race - one thread loops fsync() while another loops writes/punch-hole on the same file - and the resulting bogus map is then freed deterministically by any later drop of that range.\nPR:L - Any unprivileged local user who can create and write a file on a btrfs filesystem (btrfs is the default root fs on several major distros, and /tmp or a home directory suffices) can drive the splitting and logging paths; no capabilities are required.\nUI:N - The attacker performs all the required operations itself (write, punch hole, fsync on its own file); no victim action or administrator involvement is needed.\nS:U - The corruption is confined to kernel memory within the same security authority; there is no crossing of a VM, IOMMU, or other boundary.\nC:H - The freed extent_map stays linked in the inode\u0027s modified_extents list, so later traversal in btrfs_log_changed_extents() dereferences freed slab memory; an attacker who reallocates the object controls what is read back, giving a use-after-free read primitive usable to disclose kernel memory.\nI:H - The dangling list node is written through by list_del_init()/list_add_tail() during fsync, writing attacker-influenced pointers into and from a freed heap object; such list-corruption use-after-frees are the classic basis for arbitrary write and privilege escalation.\nA:H - The bug already trips WARN_ON(!list_empty(\u0026em-\u003elist)) and then operates on freed memory, causing list corruption and an oops or panic (immediately fatal with panic_on_warn or list debugging enabled), which an unprivileged user can trigger repeatedly."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-17T05:05:39.676Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/2a9246a424f45f33a1b8367052611ebe874868ad"
},
{
"url": "https://git.kernel.org/stable/c/9304713b70e7e1450e3a76e758836fe5391bfa95"
},
{
"url": "https://git.kernel.org/stable/c/0e465c63f103a5ce6849614d6bda048d70eebec8"
},
{
"url": "https://git.kernel.org/stable/c/5eff4d5b17fa1950e80bfd1ba43dc0699e61a644"
}
],
"title": "btrfs: don\u0027t propagate EXTENT_FLAG_LOGGING to split extent maps",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-68442",
"datePublished": "2026-08-12T00:07:31.981Z",
"dateReserved": "2026-07-30T09:28:09.394Z",
"dateUpdated": "2026-08-17T05:05:39.676Z",
"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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