CVE-2026-97938
In the Linux kernel, the following vulnerability has been resolved:
reboot: fix cad_pid use-after-free race
cad_pid is a single kernel-wide struct pid pointer. proc_do_cad_pid() reads it and passes it to pid_vnr() without protecting the lifetime of the referenced struct pid. A concurrent writer can replace cad_pid and drop the final reference to the old struct pid after the reader has loaded the pointer but before pid_vnr() has finished dereferencing it, causing a use-after-free.
kill_cad_pid() has the same lifetime race when it passes cad_pid to kill_pid().
At the time this issue was reported, an unprivileged user could reach the sysctl through user and PID namespaces because cad_pid was registered in pid_table[].
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Moving cad_pid back to the global reboot sysctl table corrected that namespace and permission mismatch, but did not fix the underlying lifetime race.
Fix this by treating cad_pid as an RCU-protected pointer at both read sites and by waiting for a grace period before dropping the old reference on the write side.
call_rcu(&old_pid->rcu, ...) cannot be used here because free_pid() also queues pid->rcu; queueing the same rcu_head twice can corrupt the RCU callback list.
Detalles técnicos trazas, registros y código del informe original
Original KASAN crash stack: kernel/pid.c:545 pid_nr_ns() # reads freed pid->level kernel/pid.c:556 pid_vnr() # calls pid_nr_ns() kernel/pid.c:775 proc_do_cad_pid() # calls pid_vnr(cad_pid)
CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.20%
- Percentil entre todas las CVEs puntuadas: 9
- 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).
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-2026-97938",
"cveTags": [],
"metrics": {},
"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": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6",
"lessThan": "ae3e53fe3c1241855e3a88f74877738349948c78",
"versionType": "git"
},
{
"status": "affected",
"version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6",
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{
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"versionType": "git"
},
{
"status": "affected",
"version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6",
"lessThan": "5a88f78df753993469dab4d1831f8fb4256a9468",
"versionType": "git"
}
],
"programFiles": [
"include/linux/sched.h",
"include/linux/sched/signal.h",
"init/main.c",
"kernel/reboot.c",
"kernel/signal.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.19"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "2.6.19",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.112",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.53",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.7",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3-rc3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"include/linux/sched.h",
"include/linux/sched/signal.h",
"init/main.c",
"kernel/reboot.c",
"kernel/signal.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-09-25T11:17:21.193",
"references": [
{
"url": "https://git.kernel.org/stable/c/5a88f78df753993469dab4d1831f8fb4256a9468",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/9a17b0e053197a6a42cdc75e75a35b17aa662088",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/ad72e2566643fff7f01666d845fb026898155e1f",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/ae3e53fe3c1241855e3a88f74877738349948c78",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nreboot: fix cad_pid use-after-free race\n\ncad_pid is a single kernel-wide struct pid pointer. proc_do_cad_pid()\nreads it and passes it to pid_vnr() without protecting the lifetime of\nthe referenced struct pid. A concurrent writer can replace cad_pid and\ndrop the final reference to the old struct pid after the reader has\nloaded the pointer but before pid_vnr() has finished dereferencing it,\ncausing a use-after-free.\n\nkill_cad_pid() has the same lifetime race when it passes cad_pid to\nkill_pid().\n\nAt the time this issue was reported, an unprivileged user could reach the\nsysctl through user and PID namespaces because cad_pid was registered in\npid_table[]. Moving cad_pid back to the global reboot sysctl table\ncorrected that namespace and permission mismatch, but did not fix the\nunderlying lifetime race.\n\nFix this by treating cad_pid as an RCU-protected pointer at both read\nsites and by waiting for a grace period before dropping the old reference\non the write side.\n\ncall_rcu(&old_pid->rcu, ...) cannot be used here because free_pid()\nalso queues pid->rcu; queueing the same rcu_head twice can corrupt the\nRCU callback list.\n\nOriginal KASAN crash stack:\n kernel/pid.c:545 pid_nr_ns() # reads freed pid->level\n kernel/pid.c:556 pid_vnr() # calls pid_nr_ns()\n kernel/pid.c:775 proc_do_cad_pid() # calls pid_vnr(cad_pid)"
}
],
"lastModified": "2026-10-03T11:18:19.390",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}