CVE-2026-74506
In the Linux kernel, the following vulnerability has been resolved:
afs: Fix UAF when sending a message
In afs_make_call(), there's a race with async call reception and destruction. If a call is dispatched that doesn't have call->write_iter set (used to specify the data content for FS.StoreData), then the first rxrpc_kernel_send_data() will not set MSG_MORE in the msghdr.
Once rxrpc_send_data() queues the last request packet, the response could come in at any time and cause the call to be completed and put. However, afs_make_call() will look at the call again to see it ->write_iter should be handled - something it's only allowed to do if it has its own ref on the call. Whilst this is the case for synchronous calls, it isn't true for async calls such as FS.FetchData.
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There's also a potential UAF in afs_make_call() in the event that an asynchronous call is being sent, but the call fails in some way (e.g. it gets aborted from the server). The problem there is that afs_make_call() tries to abort a call if the rxrpc send fails, but the asynchronous notification from rxrpc may have caused the afs_call to be torn down.
generic/650 plays games with randomly taking CPUs offline, and can interject a significant delay such that the call is deallocated before afs_make_call() gets to check call->write_iter - and a UAF ensues (caught by KASAN).
Fix this by making afs_make_op_call() give the op->call its own ref rather than transferring the caller's ref to it and then dropping the ref when afs_make_call() returns.
This also means that the afs_make_call() func never loses its ref on the call now.
Detalles técnicos trazas, registros y código del informe original
BUG: KASAN: slab-use-after-free in afs_make_call+0x1c90/0x2210 [kafs] Read of size 8 at addr ffff888035e050e8 by task fsstress/1409
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 7.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.17%
- Percentil entre todas las CVEs puntuadas: 6
- 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
T1068Exploitation for Privilege Escalationprivilege escalation85 % - Impacto principal
T1005Data from Local Systemcollection75 % - Impacto secundario
T1499.004Application or System Exploitationimpact65 %
UAF local con PR:L permite escalada o lectura de memoria kernel. El fallo de referencia en afs_make_call() tras despacho async expone datos o causa denegación de servicio.
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ 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
JSON original (NVD)
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{
"id": "CVE-2026-74506",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 7.8,
"attackVector": "LOCAL",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "HIGH"
},
"impactScore": 5.9,
"exploitabilityScore": 1.8
}
]
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"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": "e49c7b2f6de7ff81ca34c56e4eeb4fa740c099f2",
"lessThan": "c0d3b81f703b2a9e37fe1347610a50cdf0078c27",
"versionType": "git"
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{
"status": "affected",
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"lessThan": "4af1ec68d54b3871155914d584fb10669c41a861",
"versionType": "git"
}
],
"programFiles": [
"fs/afs/internal.h"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "5.8"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "5.8",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.18.44",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.8",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/afs/internal.h"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-08-15T13:17:55.630",
"references": [
{
"url": "https://git.kernel.org/stable/c/4af1ec68d54b3871155914d584fb10669c41a861",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
"url": "https://git.kernel.org/stable/c/c0d3b81f703b2a9e37fe1347610a50cdf0078c27",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/daaa726b14fc3026a6b328614d312b698f62f391",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nafs: Fix UAF when sending a message\n\nIn afs_make_call(), there's a race with async call reception and\ndestruction. If a call is dispatched that doesn't have call->write_iter\nset (used to specify the data content for FS.StoreData), then the first\nrxrpc_kernel_send_data() will not set MSG_MORE in the msghdr.\n\nOnce rxrpc_send_data() queues the last request packet, the response could\ncome in at any time and cause the call to be completed and put. However,\nafs_make_call() will look at the call again to see it ->write_iter should\nbe handled - something it's only allowed to do if it has its own ref on the\ncall. Whilst this is the case for synchronous calls, it isn't true for\nasync calls such as FS.FetchData.\n\nThere's also a potential UAF in afs_make_call() in the event that an\nasynchronous call is being sent, but the call fails in some way (e.g. it\ngets aborted from the server). The problem there is that afs_make_call()\ntries to abort a call if the rxrpc send fails, but the asynchronous\nnotification from rxrpc may have caused the afs_call to be torn down.\n\ngeneric/650 plays games with randomly taking CPUs offline, and can\ninterject a significant delay such that the call is deallocated before\nafs_make_call() gets to check call->write_iter - and a UAF ensues (caught\nby KASAN).\n\n BUG: KASAN: slab-use-after-free in afs_make_call+0x1c90/0x2210 [kafs]\n Read of size 8 at addr ffff888035e050e8 by task fsstress/1409\n\nFix this by making afs_make_op_call() give the op->call its own ref rather\nthan transferring the caller's ref to it and then dropping the ref when\nafs_make_call() returns.\n\nThis also means that the afs_make_call() func never loses its ref on the\ncall now."
}
],
"lastModified": "2026-08-17T06:19:47.137",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}