CVE-2026-68148 (GCVE-0-2026-68148)
Vulnerability from cvelistv5
Published
2026-08-10 11:59
Modified
2026-08-19 16:30
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
fscrypt: Add missing superblock check in find_or_insert_direct_key()
The legacy 'fscrypt_direct_keys' table caches master keys that are used
by v1 encryption policies that have FSCRYPT_POLICY_FLAG_DIRECT_KEY.
It's just a global table for all filesystems (since the keys can be
provided by the legacy process-subscribed keyrings mechanism, which
makes it difficult to reuse super_block::s_master_keys).
The entries in it ('struct fscrypt_direct_key') do contain a super_block
pointer, though, for passing to fscrypt_destroy_inline_crypt_key() when
the last inode that references the key is evicted.
However, when finding the fscrypt_direct_key for an inode, we weren't
actually comparing the super_block pointer. As a result, inodes with
different super_blocks could point to the same fscrypt_direct_key. That
could extend the lifetime of a fscrypt_direct_key beyond the
super_block it points to, causing a use-after-free later.
Fix this by creating distinct fscrypt_direct_key structs for distinct
super_block structs.
Note that this problem doesn't exist in the v2 policy equivalent
("per-mode keys"), since the data structures there are per super_block.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 22e9947a4b2ba255888541bd0111cf00b9b16586 Version: 22e9947a4b2ba255888541bd0111cf00b9b16586 Version: 22e9947a4b2ba255888541bd0111cf00b9b16586 Version: 22e9947a4b2ba255888541bd0111cf00b9b16586 Version: 22e9947a4b2ba255888541bd0111cf00b9b16586 Version: 22e9947a4b2ba255888541bd0111cf00b9b16586 |
||
{
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{
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"versionType": "original_commit_for_fix"
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}
],
"cpeApplicability": [
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfscrypt: Add missing superblock check in find_or_insert_direct_key()\n\nThe legacy \u0027fscrypt_direct_keys\u0027 table caches master keys that are used\nby v1 encryption policies that have FSCRYPT_POLICY_FLAG_DIRECT_KEY.\nIt\u0027s just a global table for all filesystems (since the keys can be\nprovided by the legacy process-subscribed keyrings mechanism, which\nmakes it difficult to reuse super_block::s_master_keys).\n\nThe entries in it (\u0027struct fscrypt_direct_key\u0027) do contain a super_block\npointer, though, for passing to fscrypt_destroy_inline_crypt_key() when\nthe last inode that references the key is evicted.\n\nHowever, when finding the fscrypt_direct_key for an inode, we weren\u0027t\nactually comparing the super_block pointer. As a result, inodes with\ndifferent super_blocks could point to the same fscrypt_direct_key. That\ncould extend the lifetime of a fscrypt_direct_key beyond the\nsuper_block it points to, causing a use-after-free later.\n\nFix this by creating distinct fscrypt_direct_key structs for distinct\nsuper_block structs.\n\nNote that this problem doesn\u0027t exist in the v2 policy equivalent\n(\"per-mode keys\"), since the data structures there are per super_block."
}
],
"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 flaw is reached only through local syscalls (mount/umount, FS_IOC_SET_ENCRYPTION_POLICY, and file I/O that calls fscrypt_get_encryption_info -\u003e find_or_insert_direct_key); fscrypt is not invoked from network-facing kernel services.\nAC:L - An attacker who can mount two encrypted filesystems with the same v1 DIRECT_KEY master key, share the global cache entry, then unmount the first superblock can deterministically trigger eviction-time cleanup on a freed super_block without races or victim-dependent timing.\nPR:L - Exploitation requires mounting/unmounting filesystems and setting v1 DIRECT_KEY policies (CAP_SYS_ADMIN in a user/mount namespace) or supplying keys via process keyrings; per kernel guidance, CAP_SYS_ADMIN obtainable in user namespaces maps to PR:L.\nUI:N - No separate victim action is required; the attacker sets v1 DIRECT_KEY policies, accesses encrypted inodes on two mounts, and controls unmount/eviction to hit the vulnerable refcount and cleanup path.\nS:U - The use-after-free corrupts kernel heap memory and enables local privilege escalation within the same kernel; it does not cross VM, hypervisor, or IOMMU security boundaries.\nC:H - Extending a fscrypt_direct_key past its super_block lifetime causes cleanup to dereference a freed super_block in fscrypt_destroy_inline_crypt_key(), a use-after-free that can leak kernel memory and support arbitrary-read exploitation primitives.\nI:H - Use-after-free during inline-crypto key destruction on a dangling super_block pointer can be leveraged for heap corruption and arbitrary kernel writes, enabling local privilege escalation rather than only a controlled crash.\nA:H - Evicting the last inode holding the mismatched fscrypt_direct_key dereferences a freed super_block during key teardown, which can cause kernel oops/panic and complete local denial of service on encrypted mobile/embedded and server systems using inline encryption."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-19T16:30:13.417Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
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"references": [
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"url": "https://git.kernel.org/stable/c/965b5bc8cf5031225e057979ce660fec2bd5fbfc"
},
{
"url": "https://git.kernel.org/stable/c/330249609b70778094a7a36f5b6bcfa6362121d4"
},
{
"url": "https://git.kernel.org/stable/c/deff41898a5ae3a47db5fa1896a494aa95efda5d"
},
{
"url": "https://git.kernel.org/stable/c/95376fe9c145be35566991df99c53134943d992f"
},
{
"url": "https://git.kernel.org/stable/c/466f187b501a5ac8e1ea2ccf3ccd5c46108d8830"
},
{
"url": "https://git.kernel.org/stable/c/b5fa40226e71c17847b9ff2816c6ca4133d0d994"
}
],
"title": "fscrypt: Add missing superblock check in find_or_insert_direct_key()",
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"cveMetadata": {
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"assignerShortName": "Linux",
"cveId": "CVE-2026-68148",
"datePublished": "2026-08-10T11:59:13.413Z",
"dateReserved": "2026-07-30T09:28:09.371Z",
"dateUpdated": "2026-08-19T16:30:13.417Z",
"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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