CVE-2026-74628 (GCVE-0-2026-74628)
Vulnerability from cvelistv5
Published
2026-08-22 15:32
Modified
2026-08-27 12:39
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
net/x25: fix use-after-free of the socket by its timers
The x25 timers are armed with mod_timer() and cancelled with
timer_delete(), so a pending timer holds no reference on the socket and a
cancel does not wait for a callback already running on another CPU.
x25_heartbeat_expiry() also rearms unconditionally, so it can reinstall
sk->sk_timer after __x25_destroy_socket() has passed its cancel point.
The following __sock_put() frees the socket while the timer is still
queued, and the next expiry uses freed memory. KASAN reports a
slab-use-after-free on the kmalloc-2k object freed by close().
timer_delete_sync() cannot be used here: x25_heartbeat_expiry() and
x25_timer_expiry() both reach the cancels from inside the timer they
would wait on, through __x25_destroy_socket() and x25_disconnect().
Arm the timers with sk_reset_timer() and cancel them with sk_stop_timer()
so that an armed timer owns a reference, and release it in both expiry
handlers. Rearm the heartbeat only while sk_hashed(sk) is still true,
since __x25_destroy_socket() unlinks the socket before dropping it. Arm
the deferred destroy timer the same way and drop its reference in
x25_destroy_timer().
Reproduced on net with KASAN, with the heartbeat period shortened so the
window recurs. With this patch the reproducer no longer triggers a
report and /proc/net/x25 drains.
Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/x25/af_x25.c",
"net/x25/x25_timer.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
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"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
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"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
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"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
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"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
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},
{
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"versionType": "git"
},
{
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"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
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"status": "affected",
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"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/x25/af_x25.c",
"net/x25/x25_timer.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.12"
},
{
"lessThan": "2.6.12",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.267",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.217",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.184",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.153",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.105",
"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": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.267",
"versionStartIncluding": "2.6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "2.6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.184",
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"vulnerable": true
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{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"vulnerable": true
},
{
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"versionStartIncluding": "2.6.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.45",
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.9",
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},
{
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"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/x25: fix use-after-free of the socket by its timers\n\nThe x25 timers are armed with mod_timer() and cancelled with\ntimer_delete(), so a pending timer holds no reference on the socket and a\ncancel does not wait for a callback already running on another CPU.\n\nx25_heartbeat_expiry() also rearms unconditionally, so it can reinstall\nsk-\u003esk_timer after __x25_destroy_socket() has passed its cancel point.\nThe following __sock_put() frees the socket while the timer is still\nqueued, and the next expiry uses freed memory. KASAN reports a\nslab-use-after-free on the kmalloc-2k object freed by close().\n\ntimer_delete_sync() cannot be used here: x25_heartbeat_expiry() and\nx25_timer_expiry() both reach the cancels from inside the timer they\nwould wait on, through __x25_destroy_socket() and x25_disconnect().\n\nArm the timers with sk_reset_timer() and cancel them with sk_stop_timer()\nso that an armed timer owns a reference, and release it in both expiry\nhandlers. Rearm the heartbeat only while sk_hashed(sk) is still true,\nsince __x25_destroy_socket() unlinks the socket before dropping it. Arm\nthe deferred destroy timer the same way and drop its reference in\nx25_destroy_timer().\n\nReproduced on net with KASAN, with the heartbeat period shortened so the\nwindow recurs. With this patch the reproducer no longer triggers a\nreport and /proc/net/x25 drains.\n\nDiscovered by XBOW, triaged by Baul Lee \u003cbaul.lee@xbow.com\u003e"
}
],
"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 - Remote X.25 frames reach x25_lapb_receive_frame() on init_net gateways, where unauthenticated CALL_REQUEST/CLEAR handling arms heartbeat timers and drives server socket teardown through __x25_destroy_socket() during close.\nAC:L - The attacker controls both sides of the race by opening/closing sockets or sending concurrent connect/clear traffic, repeatedly forcing __x25_destroy_socket() against sk_timer callbacks that re-arm via mod_timer().\nPR:N - X.25 call setup and clearing are unauthenticated on the wire; a remote peer can create sockets via CALL_REQUEST and force teardown without any local account or CAP_NET_ADMIN.\nUI:N - Exploitation requires no end-user action; automated server handling of remote X.25 connect/clear suffices to reach the vulnerable close/timer path.\nS:U - Impact stays within kernel memory via standard slab UAF on the AF_X25 socket object; this is not a guest/host or IOMMU boundary escape.\nC:H - KASAN reports slab-use-after-free on the kmalloc-2k socket freed by close(), and UAF on struct sock gives attacker-controlled reuse enabling arbitrary kernel memory disclosure.\nI:H - Use-after-free of the socket structure enables heap grooming and corrupting freed object contents for control-flow or arbitrary kernel writes/code execution.\nA:H - The freed socket timer expiry dereferences released memory and can oops/panic the kernel; UAF reliably threatens system availability even before full exploitation."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-27T12:39:49.703Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/ba925a2e98ce967a0e71c5bcbcf5dbd3facaf0c8"
},
{
"url": "https://git.kernel.org/stable/c/6b79659590f0f82a9b8efd2ffd55ec6399ebfc33"
},
{
"url": "https://git.kernel.org/stable/c/fdd9ac50b9b61ef2b2d52c5156aff788be91454d"
},
{
"url": "https://git.kernel.org/stable/c/1fc9f6d2c7c9fdb341bfe8ca449c990632299ea6"
},
{
"url": "https://git.kernel.org/stable/c/3c4919be5d910db4beebca420953858606fba7d8"
},
{
"url": "https://git.kernel.org/stable/c/4bc522b33438fefc3272840ae5988771863a4f1f"
},
{
"url": "https://git.kernel.org/stable/c/e92c7e2b41d1528a830bc64c5e4e46dfa8133dda"
},
{
"url": "https://git.kernel.org/stable/c/2195424c3da2ef1829a63b807e3a900a90e57d85"
}
],
"title": "net/x25: fix use-after-free of the socket by its timers",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74628",
"datePublished": "2026-08-22T15:32:10.135Z",
"dateReserved": "2026-08-15T05:44:03.921Z",
"dateUpdated": "2026-08-27T12:39:49.703Z",
"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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