FKIE_CVE-2026-89654
Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-09-13 07:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved:
ceph: fix UAF in check_new_map() on session freed during unlock
check_new_map() iterates mdsc->sessions[] and for each active session
drops mdsc->mutex to perform per-session operations. The forced-close
path (rank removed from map) correctly takes a reference on s via
ceph_get_mds_session() before releasing mdsc->mutex, but three other
paths do not:
Path A (address changed): mutex_unlock → mutex_lock(&s->s_mutex)
Path B (reconnect): mutex_unlock → send_mds_reconnect(mdsc, s)
Path C (active transition): mutex_unlock → mutex_lock(&s->s_mutex)
Without the extra reference, another thread can acquire mdsc->mutex
during the unlock window, call __unregister_session() which drops the
last reference on s, and free it. The original thread then accesses
freed memory via s->s_mutex.
Fix by adding ceph_get_mds_session(s) before each mutex_unlock and
ceph_put_mds_session(s) after the corresponding mutex_lock, matching
the pattern already used in the forced-close path.
Race timeline (Path A):
Thread A (check_new_map) Thread B (another map update
holds mdsc->mutex or session teardown)
-------------------------- --------------------------
s = mdsc->sessions[i]
(refcount == 1, held only by
sessions[] array)
mutex_unlock(&mdsc->mutex)
---> acquires mdsc->mutex
__unregister_session(mdsc, s)
sessions[i] = NULL
ceph_put_mds_session(s)
refcount: 1 -> 0
kfree(s) <--- freed!
mutex_lock(&s->s_mutex)
UAF on freed s->s_mutex
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/ceph/mds_client.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "21d5be092d947f8d83f76f7ebf3989e7e9230a98",
"status": "affected",
"version": "2f2dc053404febedc9c273452d9d518fb31fde72",
"versionType": "git"
},
{
"lessThan": "ee611a7509554c4ca1f54f6aefe592fb1df7ea70",
"status": "affected",
"version": "2f2dc053404febedc9c273452d9d518fb31fde72",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"fs/ceph/mds_client.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.34"
},
{
"lessThan": "2.6.34",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.2.*",
"status": "unaffected",
"version": "7.2.4",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3-rc1",
"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\nceph: fix UAF in check_new_map() on session freed during unlock\n\ncheck_new_map() iterates mdsc-\u003esessions[] and for each active session\ndrops mdsc-\u003emutex to perform per-session operations. The forced-close\npath (rank removed from map) correctly takes a reference on s via\nceph_get_mds_session() before releasing mdsc-\u003emutex, but three other\npaths do not:\n\n Path A (address changed): mutex_unlock \u2192 mutex_lock(\u0026s-\u003es_mutex)\n Path B (reconnect): mutex_unlock \u2192 send_mds_reconnect(mdsc, s)\n Path C (active transition): mutex_unlock \u2192 mutex_lock(\u0026s-\u003es_mutex)\n\nWithout the extra reference, another thread can acquire mdsc-\u003emutex\nduring the unlock window, call __unregister_session() which drops the\nlast reference on s, and free it. The original thread then accesses\nfreed memory via s-\u003es_mutex.\n\nFix by adding ceph_get_mds_session(s) before each mutex_unlock and\nceph_put_mds_session(s) after the corresponding mutex_lock, matching\nthe pattern already used in the forced-close path.\n\nRace timeline (Path A):\n\n Thread A (check_new_map) Thread B (another map update\n holds mdsc-\u003emutex or session teardown)\n -------------------------- --------------------------\n s = mdsc-\u003esessions[i]\n (refcount == 1, held only by\n sessions[] array)\n\n mutex_unlock(\u0026mdsc-\u003emutex)\n ---\u003e acquires mdsc-\u003emutex\n __unregister_session(mdsc, s)\n sessions[i] = NULL\n ceph_put_mds_session(s)\n refcount: 1 -\u003e 0\n kfree(s) \u003c--- freed!\n\n mutex_lock(\u0026s-\u003es_mutex)\n UAF on freed s-\u003es_mutex"
}
],
"id": "CVE-2026-89654",
"lastModified": "2026-09-13T07:17:30.837",
"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": "2026-09-11T20:19:51.540",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/21d5be092d947f8d83f76f7ebf3989e7e9230a98"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/ee611a7509554c4ca1f54f6aefe592fb1df7ea70"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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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.
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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.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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