FKIE_CVE-2026-74628
Vulnerability from fkie_nvd - Published: 2026-08-22 16:16 - Updated: 2026-08-27 13:18
Severity
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 |
|---|
{
"affected": [
{
"affectedData": [
{
"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": [
{
"lessThan": "ba925a2e98ce967a0e71c5bcbcf5dbd3facaf0c8",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "6b79659590f0f82a9b8efd2ffd55ec6399ebfc33",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "fdd9ac50b9b61ef2b2d52c5156aff788be91454d",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "1fc9f6d2c7c9fdb341bfe8ca449c990632299ea6",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "3c4919be5d910db4beebca420953858606fba7d8",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "4bc522b33438fefc3272840ae5988771863a4f1f",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "e92c7e2b41d1528a830bc64c5e4e46dfa8133dda",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"versionType": "git"
},
{
"lessThan": "2195424c3da2ef1829a63b807e3a900a90e57d85",
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"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"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"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"
}
],
"id": "CVE-2026-74628",
"lastModified": "2026-08-27T13:18:34.940",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
]
},
"published": "2026-08-22T16:16:35.737",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/1fc9f6d2c7c9fdb341bfe8ca449c990632299ea6"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/2195424c3da2ef1829a63b807e3a900a90e57d85"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/3c4919be5d910db4beebca420953858606fba7d8"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/4bc522b33438fefc3272840ae5988771863a4f1f"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/6b79659590f0f82a9b8efd2ffd55ec6399ebfc33"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/ba925a2e98ce967a0e71c5bcbcf5dbd3facaf0c8"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/e92c7e2b41d1528a830bc64c5e4e46dfa8133dda"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/fdd9ac50b9b61ef2b2d52c5156aff788be91454d"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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