CVE-2026-74692 (GCVE-0-2026-74692)
Vulnerability from cvelistv5
Published
2026-08-22 15:32
Modified
2026-08-25 05:41
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
net/smc: fix TOCTOU race between smc_listen_out() and listener close
smc_listen_out() reads lsmc->sk.sk_state without the listener lock,
then acquires lock_sock_nested() only after the check passes. This
opens a window where smc_close_active() can transition the listener
to SMC_CLOSED, call smc_close_cleanup_listen() to drain the accept
queue, and release the lock, all between the lockless read and the
delayed lock acquisition:
smc_listen_work (smc_hs_wq) smc_close_active()
------------------------------- -------------------------
release_sock(child)
if (sk_state == SMC_LISTEN) TRUE
lock_sock(listener)
sk_state = SMC_CLOSED
smc_close_cleanup_listen()
release_sock(listener)
flush_work(tcp_listen_work)
lock_sock_nested(listener)
smc_accept_enqueue(listener, child) /* child enqueued on dead listener */
smc_close_active() flushes only tcp_listen_work. Work items already
dispatched onto smc_hs_wq for the CLC handshake continue running
unguarded. smc_accept_enqueue() takes a sock_hold() on the child that
is never released, so the child smc_sock, its clcsock, and the
reference all leak. A remote peer that opens TCP connections while the
server calls close() can exhaust kernel memory.
Move lock_sock_nested() to before the sk_state check so that the test
and the enqueue are atomic under the listener lock.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9 Version: fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9 Version: fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9 Version: fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9 Version: fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9 Version: fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9 Version: fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9 Version: d1d004585b40c212b338fc8a40cbaaf230ea4703 Version: 4.19.299 ≤ |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/smc/af_smc.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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"version": "fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9",
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},
{
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},
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "5.1"
},
{
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"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.216",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.152",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.104",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.45",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.9",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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}
],
"negate": false,
"operator": "OR"
}
]
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix TOCTOU race between smc_listen_out() and listener close\n\nsmc_listen_out() reads lsmc-\u003esk.sk_state without the listener lock,\nthen acquires lock_sock_nested() only after the check passes. This\nopens a window where smc_close_active() can transition the listener\nto SMC_CLOSED, call smc_close_cleanup_listen() to drain the accept\nqueue, and release the lock, all between the lockless read and the\ndelayed lock acquisition:\n\n smc_listen_work (smc_hs_wq) smc_close_active()\n ------------------------------- -------------------------\n release_sock(child)\n if (sk_state == SMC_LISTEN) TRUE\n lock_sock(listener)\n sk_state = SMC_CLOSED\n smc_close_cleanup_listen()\n release_sock(listener)\n flush_work(tcp_listen_work)\n lock_sock_nested(listener)\n smc_accept_enqueue(listener, child) /* child enqueued on dead listener */\n\nsmc_close_active() flushes only tcp_listen_work. Work items already\ndispatched onto smc_hs_wq for the CLC handshake continue running\nunguarded. smc_accept_enqueue() takes a sock_hold() on the child that\nis never released, so the child smc_sock, its clcsock, and the\nreference all leak. A remote peer that opens TCP connections while the\nserver calls close() can exhaust kernel memory.\n\nMove lock_sock_nested() to before the sk_state check so that the test\nand the enqueue are atomic under the listener lock."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.5,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The bug fires when smc_listen_work() on smc_hs_wq finishes an inbound SMC/TCP handshake queued by smc_tcp_listen_work() for each remote connection to an AF_SMC listener, so any network peer that reaches the listener port drives the full path via SYN and CLC messages.\nAC:L - The attacker controls handshake completions by flooding SMC-capable TCP connections and overlapping them with listener close(), either by timing floods against restarts or locally by running server and client together; smc_close_active() only flushes tcp_listen_work, leaving smc_hs_wq workers racing through the unlocked sk_state check.\nPR:N - SMC performs no authentication; smc_create() and smc_listen() enforce no capabilities, and smc_listen_work() processes the CLC handshake immediately after TCP accept before any credential verification, so an unauthenticated remote peer need only reach the listener port.\nUI:N - Exploitation requires only inbound network connections and kernel handshake/close processing; no end-user action such as opening a file or mounting a filesystem is needed, and listener shutdown during deployments or restarts is routine automated server behavior.\nS:U - The leak accumulates orphaned smc_sock structures and clcsock references within the kernel networking subsystem on the targeted host; it does not cross VM, container, IOMMU, or other security boundaries.\nC:N - The bug is an unreleased sock_hold() leaving child sockets on a closed listener accept queue; objects are never freed prematurely, so there is no out-of-bounds read, use-after-free dereference, or kernel data disclosure to the attacker.\nI:N - Only reference counts are incremented without matching decrements; no memory is written out of bounds, no freed object is reused, and no control-flow or integrity primitive is obtained\u2014only unreclaimable kernel allocations accumulate.\nA:H - Each successful race permanently leaks a child smc_sock, its clcsock, and sock references that smc_close_cleanup_listen() can never drain; a remote peer repeating handshakes during listener close can exhaust kernel memory and cause system-wide denial of service."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-25T05:41:37.608Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/53c7938d8bcfde3296ec1a347ba2a9393c1fdcfa"
},
{
"url": "https://git.kernel.org/stable/c/feb71634bb1abab3e8fb5cde874b27001cc1282e"
},
{
"url": "https://git.kernel.org/stable/c/01865e1ddb126b25ac9eba5cdd7ec49e11183a64"
},
{
"url": "https://git.kernel.org/stable/c/00f89433777236ced4771211047fb5d4cd581cea"
},
{
"url": "https://git.kernel.org/stable/c/78e5ebcd1c10ed7c8bda0a99e0abd5b62da86d67"
},
{
"url": "https://git.kernel.org/stable/c/ff5bcd804b5bc5c64736b7d318c20e12ea9506b8"
},
{
"url": "https://git.kernel.org/stable/c/185a4caeecabc150106deda1da170b09f2ad803f"
}
],
"title": "net/smc: fix TOCTOU race between smc_listen_out() and listener close",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74692",
"datePublished": "2026-08-22T15:32:55.873Z",
"dateReserved": "2026-08-15T05:44:03.926Z",
"dateUpdated": "2026-08-25T05:41:37.608Z",
"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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