CVE-2026-89655
Estado: RecibidaCrítica (9.8)—
In the Linux kernel, the following vulnerability has been resolved:
ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
list_for_each_entry() iterates ci->i_cap_flush_list but drops i_ceph_lock to send cap messages. During the unlock window, handle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries with tid <= flush_tid from the list, release i_ceph_lock, and free them via ceph_free_cap_flush() outside any lock. When the original thread reacquires i_ceph_lock and the for-loop macro advances via cf = list_next_entry(cf, i_list), it dereferences cf->i_list.next on freed memory.
Leer descripción completaMostrar menos
The race timeline:
The cf was just sent by __kick_flushing_caps itself via __send_cap(). The MDS may respond with FLUSH_ACK quickly enough that handle_cap_flush_ack() frees cf before __kick_flushing_caps can finish the iteration.
Fix by converting to a manual while loop: save the next pointer under i_ceph_lock before dropping it, then use the saved pointer after reacquiring, so the potentially-freed cf is never accessed again.
Detalles técnicos trazas, registros y código del informe original
__kick_flushing_caps() handle_cap_flush_ack()
----------------------- -----------------------
holds i_ceph_lock <---
iterates to cf (tid=10)
prepares FLUSH message
drops i_ceph_lock <---
__send_cap() ── FLUSH(tid=10)
MDS sends FLUSH_ACK(tid=10)
---> acquires i_ceph_lock
cf->tid(10) <= flush_tid(10),
detaches cf from i_cap_flush_list
drops i_ceph_lock
ceph_free_cap_flush(cf) <- frees it!
acquires i_ceph_lock <---
for-loop advances:
cf = list_next_entry(cf, i_list)
-- UAF on freed cf->i_list.nextCVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 9.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.71%
- Percentil entre todas las CVEs puntuadas: 52
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1190Exploit Public-Facing Applicationinitial access60 %
Inferido por reglas deterministas a partir del vector CVSS y la CWE. Solo orientativo.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
- https://git.kernel.org/stable/c/01542430081014d80fc9e70e92d6647432ddb7fc
- https://git.kernel.org/stable/c/091137821e1fc88f37e15201abf055c9494ddc61
- https://git.kernel.org/stable/c/19f16f04c2b014a7dd214dc1e42557d8530b16f3
- https://git.kernel.org/stable/c/23eb34a53a53cb1a6dab1eeee830633207ac158d
- https://git.kernel.org/stable/c/2701431aa3cc8b23efe6890182e7b04f5e76fab5
- https://git.kernel.org/stable/c/2dba24dcd5050be4b7b119e6f0b01f62203b5d26
- https://git.kernel.org/stable/c/7af4c4f01305b0935adf6d4301b1ec407025485d
- https://git.kernel.org/stable/c/fe46746087b5b9c5bb2d022df6c7819218494ced
JSON original (NVD)
Mostrar
{
"id": "CVE-2026-89655",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 9.8,
"attackVector": "NETWORK",
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "NONE",
"confidentialityImpact": "HIGH"
},
"impactScore": 5.9,
"exploitabilityScore": 3.9
}
]
},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "e4500b5e35c213e0f97be7cb69328c0877203a79",
"lessThan": "091137821e1fc88f37e15201abf055c9494ddc61",
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{
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],
"programFiles": [
"fs/ceph/caps.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.8"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.8",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.270",
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},
{
"status": "unaffected",
"version": "5.15.221",
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},
{
"status": "unaffected",
"version": "6.1.188",
"versionType": "semver",
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},
{
"status": "unaffected",
"version": "6.6.157",
"versionType": "semver",
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},
{
"status": "unaffected",
"version": "6.12.109",
"versionType": "semver",
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},
{
"status": "unaffected",
"version": "6.18.50",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.4",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3-rc1",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/ceph/caps.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-09-11T20:19:51.683",
"references": [
{
"url": "https://git.kernel.org/stable/c/01542430081014d80fc9e70e92d6647432ddb7fc",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/23eb34a53a53cb1a6dab1eeee830633207ac158d",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/2701431aa3cc8b23efe6890182e7b04f5e76fab5",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/2dba24dcd5050be4b7b119e6f0b01f62203b5d26",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/7af4c4f01305b0935adf6d4301b1ec407025485d",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/fe46746087b5b9c5bb2d022df6c7819218494ced",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock\n\nlist_for_each_entry() iterates ci->i_cap_flush_list but drops\ni_ceph_lock to send cap messages. During the unlock window,\nhandle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries\nwith tid <= flush_tid from the list, release i_ceph_lock, and free\nthem via ceph_free_cap_flush() outside any lock. When the original\nthread reacquires i_ceph_lock and the for-loop macro advances via\ncf = list_next_entry(cf, i_list), it dereferences cf->i_list.next\non freed memory.\n\nThe race timeline:\n\n __kick_flushing_caps() handle_cap_flush_ack()\n ----------------------- -----------------------\n holds i_ceph_lock <---\n iterates to cf (tid=10)\n prepares FLUSH message\n drops i_ceph_lock <---\n __send_cap() ── FLUSH(tid=10)\n\t MDS sends FLUSH_ACK(tid=10)\n ---> acquires i_ceph_lock\n cf->tid(10) <= flush_tid(10),\n detaches cf from i_cap_flush_list\n drops i_ceph_lock\n ceph_free_cap_flush(cf) <- frees it!\n acquires i_ceph_lock <---\n for-loop advances:\n cf = list_next_entry(cf, i_list)\n -- UAF on freed cf->i_list.next\n\nThe cf was just sent by __kick_flushing_caps itself via __send_cap().\nThe MDS may respond with FLUSH_ACK quickly enough that\nhandle_cap_flush_ack() frees cf before __kick_flushing_caps can\nfinish the iteration.\n\nFix by converting to a manual while loop: save the next pointer\nunder i_ceph_lock before dropping it, then use the saved pointer\nafter reacquiring, so the potentially-freed cf is never accessed again."
}
],
"lastModified": "2026-09-14T13:19:17.913",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}