CVE-2026-74363 (GCVE-0-2026-74363)
Vulnerability from cvelistv5
Published
2026-08-15 05:58
Modified
2026-08-17 05:46
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
bpf: fix UAF by restoring RCU-delayed inode freeing in bpffs
commit 4f375ade6aa9 ("bpf: Avoid RCU context warning when unpinning
htab with internal structs") moved inode cleanup from ->free_inode()
into ->destroy_inode() to avoid sleeping in RCU context when calling
bpf_any_put(). However this removed the RCU delay on freeing the
inode itself and the cached symlink body (i_link), both of which
can be accessed by RCU pathwalk (pick_link, may_lookup etc.).
This causes a use-after-free when a concurrent unlinkat() drops the
last inode reference and destroy_inode() frees the inode immediately,
while another task is still walking the path in RCU mode and reads
inode->i_opflags (offset +2) inside current_time() -> is_mgtime().
KASAN reports:
BUG: KASAN: slab-use-after-free in is_mgtime include/linux/fs.h:2313
Read of size 2 at addr ffff8880407e4282 (offset +2 = i_opflags)
The rules (per Al Viro):
->destroy_inode() called immediately, can sleep, use for blocking
cleanup e.g. bpf_any_put()
->free_inode() called after RCU grace period, use for freeing
inode and anything RCU-accessible e.g. i_link
Fix: split the two concerns properly:
- keep bpf_any_put() in bpf_destroy_inode() since it is blocking
and needs to run promptly
- introduce bpf_free_inode() to handle kfree(i_link) and
free_inode_nonrcu() with proper RCU delay, preventing the UAF
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: e28616ca3d67e745ecb2f10eba4a626e1fc9a203 Version: 743a620c661994c7f0938e6dd32fb0883fb1e0ea Version: b6e9645be9eb93f7aff3ca887f8edb6f1d63358f Version: ee04cff9ed4d6bb25802f5cecfcd0750500410f3 Version: 4f375ade6aa9f37fd72d7a78682f639772089eed Version: 4f375ade6aa9f37fd72d7a78682f639772089eed Version: 4f375ade6aa9f37fd72d7a78682f639772089eed Version: de2d2baecc84cc7fca52eec2b9b55d89c93e3565 Version: 5.15.195 ≤ Version: 6.1.157 ≤ Version: 6.6.113 ≤ Version: 6.12.54 ≤ Version: 6.17.4 ≤ |
||
{
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],
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"vendor": "Linux",
"versions": [
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{
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{
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{
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"cpeApplicability": [
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: fix UAF by restoring RCU-delayed inode freeing in bpffs\n\ncommit 4f375ade6aa9 (\"bpf: Avoid RCU context warning when unpinning\nhtab with internal structs\") moved inode cleanup from -\u003efree_inode()\ninto -\u003edestroy_inode() to avoid sleeping in RCU context when calling\nbpf_any_put(). However this removed the RCU delay on freeing the\ninode itself and the cached symlink body (i_link), both of which\ncan be accessed by RCU pathwalk (pick_link, may_lookup etc.).\n\nThis causes a use-after-free when a concurrent unlinkat() drops the\nlast inode reference and destroy_inode() frees the inode immediately,\nwhile another task is still walking the path in RCU mode and reads\ninode-\u003ei_opflags (offset +2) inside current_time() -\u003e is_mgtime().\n\nKASAN reports:\n BUG: KASAN: slab-use-after-free in is_mgtime include/linux/fs.h:2313\n Read of size 2 at addr ffff8880407e4282 (offset +2 = i_opflags)\n\nThe rules (per Al Viro):\n -\u003edestroy_inode() called immediately, can sleep, use for blocking\n cleanup e.g. bpf_any_put()\n -\u003efree_inode() called after RCU grace period, use for freeing\n inode and anything RCU-accessible e.g. i_link\n\nFix: split the two concerns properly:\n - keep bpf_any_put() in bpf_destroy_inode() since it is blocking\n and needs to run promptly\n - introduce bpf_free_inode() to handle kfree(i_link) and\n free_inode_nonrcu() with proper RCU delay, preventing the UAF"
}
],
"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 triggered through local VFS and bpf(2) syscalls on bpffs (unlinkat/symlinkat/openat/stat and BPF_OBJ_GET/BPF_OBJ_PIN) racing RCU pathwalk; BPF/bpffs is not reachable from remote network services.\nAC:L - Exploitation requires a race between unlinkat dropping the last bpffs inode reference and concurrent RCU pathwalk, but the attacker controls both sides with parallel threads/syscalls and syzbot reliably reproduces the UAF without external timing.\nPR:L - Any local user with write access to a bpffs mount (default sticky world-writable /sys/fs/bpf) can create symlinks or pin/unpin BPF objects without init-namespace root, including via unprivileged BPF or delegated bpffs mounts in user namespaces.\nUI:N - No victim action is required; the attacker programmatically races their own unlink/pathwalk operations on bpffs objects they can create and remove.\nS:U - This is a kernel heap use-after-free in bpffs inode lifetime management, enabling local privilege escalation within the same security domain rather than crossing VM, IOMMU, or sandbox boundaries.\nC:H - KASAN confirmed slab use-after-free reading freed inode-\u003ei_opflags during RCU pathwalk; UAF of struct inode enables subsequent arbitrary kernel memory disclosure via heap reuse.\nI:H - Premature inode freeing permits attacker-controlled heap reuse and spraying, providing a standard kernel UAF path to arbitrary write and potential code execution beyond the initial 2-byte read.\nA:H - Concurrent RCU pathwalk of a prematurely freed bpffs inode triggers KASAN slab-UAF and kernel oops; repeated triggering can panic the system or cause denial of service."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-17T05:46:21.981Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/ea1c243c39e32b7fc1c2edfe32081ff7e30a877c"
},
{
"url": "https://git.kernel.org/stable/c/5fecb71c10c28aef276ba49c718dc961745fdcf0"
},
{
"url": "https://git.kernel.org/stable/c/c70d0f9114c3cc156f6029a400c4eb7e6f7c82b2"
},
{
"url": "https://git.kernel.org/stable/c/53649846e0437d1d9b7cb993cfe54c367addf7ae"
},
{
"url": "https://git.kernel.org/stable/c/61f19729728243c82476dee31315143ed3275e7f"
},
{
"url": "https://git.kernel.org/stable/c/0497ff765746d9b2d17445c8f7cc737b36c0152a"
},
{
"url": "https://git.kernel.org/stable/c/b93c55b4932dd7e32dca8cf34a3443cc87a02906"
}
],
"title": "bpf: fix UAF by restoring RCU-delayed inode freeing in bpffs",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74363",
"datePublished": "2026-08-15T05:58:46.220Z",
"dateReserved": "2026-08-15T05:44:03.887Z",
"dateUpdated": "2026-08-17T05:46:21.981Z",
"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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