CVE-2026-74493 (GCVE-0-2026-74493)
Vulnerability from cvelistv5
Published
2026-08-15 12:27
Modified
2026-08-19 16:37
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
net/smc: fix socket use-after-free during link group termination
__smc_lgr_terminate() drops conns_lock after finding a connection in
lgr->conns_all, but before taking a reference on its socket. The connection
is embedded in the socket, and its registration reference protects it only
while the connection remains in the tree.
A concurrent close can unregister the connection and drop that reference,
freeing the socket before the termination worker reaches sock_hold().
The race is reachable when close overlaps link group termination.
Local stress testing reproduced the use-after-free and KASAN reported:
BUG: KASAN: slab-use-after-free in __smc_lgr_terminate.part.0 [smc]
Write of size 4 by task kworker/3:3
Workqueue: events smc_lgr_terminate_work [smc]
__smc_lgr_terminate.part.0 [smc]
The socket was allocated by smc_create(), freed through
slab_free_after_rcu_debug(), and was followed by:
refcount_t: addition on 0; use-after-free.
__smc_lgr_terminate.part.0 [smc]
Take the socket reference while conns_lock still protects the tree entry.
The unregister path then cannot drop the last reference until termination
has finished using the socket.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 Version: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 Version: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 Version: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 Version: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 Version: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 Version: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 Version: 69318b5215f2dc32c345a3d65b98b4b1bf29c007 |
||
{
"containers": {
"cna": {
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"programFiles": [
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{
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"version": "6.1.183",
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{
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"versionType": "original_commit_for_fix"
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}
],
"cpeApplicability": [
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"nodes": [
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix socket use-after-free during link group termination\n\n__smc_lgr_terminate() drops conns_lock after finding a connection in\nlgr-\u003econns_all, but before taking a reference on its socket. The connection\nis embedded in the socket, and its registration reference protects it only\nwhile the connection remains in the tree.\n\nA concurrent close can unregister the connection and drop that reference,\nfreeing the socket before the termination worker reaches sock_hold().\n\nThe race is reachable when close overlaps link group termination.\nLocal stress testing reproduced the use-after-free and KASAN reported:\n\n BUG: KASAN: slab-use-after-free in __smc_lgr_terminate.part.0 [smc]\n Write of size 4 by task kworker/3:3\n Workqueue: events smc_lgr_terminate_work [smc]\n __smc_lgr_terminate.part.0 [smc]\n\nThe socket was allocated by smc_create(), freed through\nslab_free_after_rcu_debug(), and was followed by:\n\n refcount_t: addition on 0; use-after-free.\n __smc_lgr_terminate.part.0 [smc]\n\nTake the socket reference while conns_lock still protects the tree entry.\nThe unregister path then cannot drop the last reference until termination\nhas finished using the socket."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The bug is hit in __smc_lgr_terminate() when a link group shuts down; that path is driven by SMC LLC control messages from a remote peer over RoCE/RDMA (smc_llc_rx_handler), including DELETE_LINK_ALL and protocol-violation termination, not only local syscalls.\nAC:L - An SMC peer can overlap link-group termination with connection teardown by sending DELETE_LINK_ALL (or a terminating LLC event) while aborting/closing the same session; the fix report shows reliable stress reproduction, and the attacker controls both sides of the terminate/close race.\nPR:N - Exploitation needs only completing an SMC handshake as a network peer to the victim; no local account, capabilities, or namespace admin rights on the victim host are required beyond normal remote connectivity to the SMC service.\nUI:N - No victim user action is needed; a remote peer can trigger termination and concurrent connection teardown purely through kernel protocol handling, without the user mounting filesystems, opening files, or performing other interactive steps.\nS:U - The impact stays within the host kernel boundary (memory corruption and potential local privilege escalation) and does not cross VM, container, or IOMMU security authorities into another trust domain.\nC:H - KASAN reported slab-use-after-free in __smc_lgr_terminate with refcount_t addition on 0 during sock_hold() on a freed smc_sock; UAF on kernel heap objects can be turned into arbitrary kernel memory disclosure via heap grooming.\nI:H - The UAF is a write of size 4 to freed socket memory during sock_hold(), giving a kernel heap corruption primitive that can be developed into arbitrary write or control-flow hijack for kernel code execution.\nA:H - The reported UAF occurs in the smc_lgr_terminate workqueue and can crash the kernel (oops/panic); repeated remote triggering against SMC/RoCE services can also cause sustained denial of service."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-19T16:37:50.842Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/ff44f2df57fb5560bdc75eb977867643e764a262"
},
{
"url": "https://git.kernel.org/stable/c/9fb17c95b8f0683570fca1fb2792264147af937a"
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{
"url": "https://git.kernel.org/stable/c/bea8dc14de2d56aca749d368563e6888217710a5"
},
{
"url": "https://git.kernel.org/stable/c/5a42f162b857019a4c10ff687dc3bcdf51831865"
},
{
"url": "https://git.kernel.org/stable/c/281c103a8eaed59001ce952f231df1b07674215a"
},
{
"url": "https://git.kernel.org/stable/c/f807a63d0d95680c34f677700da9148a07d7c78f"
},
{
"url": "https://git.kernel.org/stable/c/f0541a775d04c88e90ba448e35ce0d743512822a"
},
{
"url": "https://git.kernel.org/stable/c/f621d6ebeebb6374342571e4ddf45fdbc420f6cd"
}
],
"title": "net/smc: fix socket use-after-free during link group termination",
"x_generator": {
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"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74493",
"datePublished": "2026-08-15T12:27:21.980Z",
"dateReserved": "2026-08-15T05:44:03.906Z",
"dateUpdated": "2026-08-19T16:37:50.842Z",
"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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