CVE-2026-74686
In the Linux kernel, the following vulnerability has been resolved:
rqspinlock: Reset tail when preserving queue on deadlock
Currently, the destruction of the waiter queue is suppressed for rqspinlock in cases where a deadlock is detected. Deadlock checks happen relatively frequently (on entry for AA, within 1ms for ABBA), and waiter threads may not be involved in locking scenarios involving deadlocks. Thus, it is useful to not flush the queue and let other waiters take a stab at acquiring the lock after we detect a deadlock and exit.
However, we need to follow the same logic as what we did previously for the waitq_timeout label: reset the tail, and if we cannot, signal the next waiter appropriately.
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In case of deadlocks, this signal would just mark the MCS node as unlocked, and in case of timeouts, it would signal RES_TIMEOUT_VAL. The difference thus is in the value propagated, which decides whether the queue remains active or gets flushed.
Not doing the tail reset, and waiting for the next waiter can lead to cases where we are the final waiter, and thus no next waiter arrives, leading to intermittent stalls in this path. Once the next waiter does join, we will be unblocked. In the theoretical case when the next waiter never joins, we risk stalling indefinitely.
This can only happen for ABBA deadlocks, since entry into the wait queue is guarded with AA checks. A precise sequence of executions leading up to this scenario can be:
CPU 0 holds lock A. CPU 1 holds lock B. CPU 2 attempts lock B, becomes the pending waiter for B. CPU 0 attempts lock B. B has locked+pending bits set, thus CPU 0 queues. CPU 1 attempts lock A. CPU 0 detects an ABBA deadlock.
Once deadlock detection happens for CPU 0, it will sit waiting for the next waiter in the queue to populate node->next, which will experience delays until such a waiter arrives.
Fix this by adjusting the logic for the check for deadlocks preceding the waitq_timeout label. It would make sense to consolidate code for both cases and use 'ret' to distinguish the value being propagated, but that is left as an exercise for a future refactoring task to avoid diff noise in this patch.
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: 0.24%
- Percentil entre todas las CVEs puntuadas: 14
- 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-2026-74686",
"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": "7bd6e5ce5be666fb3fb873bf20f77e62555b7835",
"lessThan": "f54667b0c16213285c9d9b8e3929f738b8f71826",
"versionType": "git"
},
{
"status": "affected",
"version": "7bd6e5ce5be666fb3fb873bf20f77e62555b7835",
"lessThan": "7a3c0289c3c8eb4607dff448ae9ff9f902c813af",
"versionType": "git"
}
],
"programFiles": [
"kernel/bpf/rqspinlock.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.19"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.19",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "7.1.9",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"kernel/bpf/rqspinlock.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-08-22T16:16:42.973",
"references": [
{
"url": "https://git.kernel.org/stable/c/7a3c0289c3c8eb4607dff448ae9ff9f902c813af",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/f54667b0c16213285c9d9b8e3929f738b8f71826",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nrqspinlock: Reset tail when preserving queue on deadlock\n\nCurrently, the destruction of the waiter queue is suppressed for\nrqspinlock in cases where a deadlock is detected. Deadlock checks happen\nrelatively frequently (on entry for AA, within 1ms for ABBA), and waiter\nthreads may not be involved in locking scenarios involving deadlocks.\nThus, it is useful to not flush the queue and let other waiters take a\nstab at acquiring the lock after we detect a deadlock and exit.\n\nHowever, we need to follow the same logic as what we did previously for\nthe waitq_timeout label: reset the tail, and if we cannot, signal the\nnext waiter appropriately. In case of deadlocks, this signal would just\nmark the MCS node as unlocked, and in case of timeouts, it would signal\nRES_TIMEOUT_VAL. The difference thus is in the value propagated, which\ndecides whether the queue remains active or gets flushed.\n\nNot doing the tail reset, and waiting for the next waiter can lead to\ncases where we are the final waiter, and thus no next waiter arrives,\nleading to intermittent stalls in this path. Once the next waiter does\njoin, we will be unblocked. In the theoretical case when the next waiter\nnever joins, we risk stalling indefinitely.\n\nThis can only happen for ABBA deadlocks, since entry into the wait queue\nis guarded with AA checks. A precise sequence of executions leading up\nto this scenario can be:\n\nCPU 0 holds lock A.\nCPU 1 holds lock B.\nCPU 2 attempts lock B, becomes the pending waiter for B.\nCPU 0 attempts lock B. B has locked+pending bits set, thus CPU 0 queues.\nCPU 1 attempts lock A.\nCPU 0 detects an ABBA deadlock.\n\nOnce deadlock detection happens for CPU 0, it will sit waiting for the\nnext waiter in the queue to populate node->next, which will experience\ndelays until such a waiter arrives.\n\nFix this by adjusting the logic for the check for deadlocks preceding\nthe waitq_timeout label. It would make sense to consolidate code for\nboth cases and use 'ret' to distinguish the value being propagated, but\nthat is left as an exercise for a future refactoring task to avoid diff\nnoise in this patch."
}
],
"lastModified": "2026-08-22T16:16:42.973",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}