cve-2026-31555
MEDIUM CVSS 5.5 nvd
Description
In the Linux kernel, the following vulnerability has been resolved: futex: Clear stale exiting pointer in futex_lock_pi() retry path Fuzzying/stressing futexes triggered: WARNING: kernel/futex/core.c:825 at wait_for_owner_exiting+0x7a/0x80, CPU#11: futex_lock_pi_s/524 When futex_lock_pi_atomic() sees the owner is exiting, it returns -EBUSY and stores a refcounted task pointer in 'exiting'. After wait_for_owner_exiting() consumes that reference, the local pointer is never reset to nil. Upon a retry, if futex_lock_pi_atomic() returns a different error, the bogus pointer is passed to wait_for_owner_exiting(). CPU0 CPU1 CPU2 futex_lock_pi(uaddr) // acquires the PI futex exit() futex_cleanup_begin() futex_state = EXITING; futex_lock_pi(uaddr) futex_lock_pi_atomic() attach_to_pi_owner() // observes EXITING *exiting = owner; // takes ref return -EBUSY wait_for_owner_exiting(-EBUSY, owner) put_task_struct(); // drops ref // exiting still points to owner goto retry; futex_lock_pi_atomic() lock_pi_update_atomic() cmpxchg(uaddr) *uaddr ^= WAITERS // whatever // value changed return -EAGAIN; wait_for_owner_exiting(-EAGAIN, exiting) // stale WARN_ON_ONCE(exiting) Fix this by resetting upon retry, essentially aligning it with requeue_pi.
Timeline
- Published
- 2026-04-24
- Last Modified
- 2026-11-05
CVSS Details
- Attack Vector
- LOCAL
- Attack Complexity
- LOW
- Privileges Required
- LOW
Affected Products
- linux linux_kernel
CVSS metrics
| Version | Base | Severity | Vector | Exploitability | Impact | Source |
|---|---|---|---|---|---|---|
| 3.1 | 5.5 | MEDIUM | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
1.8 | 3.6 | nvd@nist.gov |
CPE configurations
OR
| CPE | Version range | Vulnerable |
|---|---|---|
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 4.4.255, < 4.5 | yes |
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 4.9.255, < 4.10 | yes |
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 4.14.158, < 4.15 | yes |
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 4.19.172, < 4.20 | yes |
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 5.4.1, < 5.5 | yes |
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 5.5.1, < 5.10.253 | yes |
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 5.11, < 5.15.203 | yes |
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 5.16, < 6.1.168 | yes |
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 6.2, < 6.6.131 | yes |
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 6.7, < 6.12.80 | yes |
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 6.13, < 6.18.21 | yes |
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
>= 6.19, < 6.19.11 | yes |
cpe:2.3:o:linux:linux_kernel:5.5:-:*:*:*:*:*:* |
— | yes |
cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:* |
— | yes |
cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:* |
— | yes |
cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:* |
— | yes |
cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:* |
— | yes |
cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:* |
— | yes |
cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:* |
— | yes |
cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:* |
— | yes |
NVD metadata
- NVD status
- Modified
- Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/210d36d892de5195e6766c45519dfb1e65f3eb83 Patch
- https://git.kernel.org/stable/c/33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa Patch
- https://git.kernel.org/stable/c/5e8e06bf8909e79b4acd950cf578cfc2f10bbefa Patch
- https://git.kernel.org/stable/c/71112e62807d1925dc3ae6188b11f8cfc85aec23 Patch
- https://git.kernel.org/stable/c/7475dfad10a05a5bfadebf5f2499bd61b19ed293 Patch
- https://git.kernel.org/stable/c/92e47ad03e03dbb5515bdf06444bf6b1e147310d Patch
- https://git.kernel.org/stable/c/de7c0c04ad868f2cee6671b11c0a6d20421af1da Patch
- https://git.kernel.org/stable/c/e7824ec168d2ac883a213cd1f4d6cc0816002a85 Patch
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html
Linked Vulnerabilities
{
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"datePublished": "2026-04-24T15:16:29.837",
"dateUpdated": "2026-11-05T22:18:40.093",
"description": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Clear stale exiting pointer in futex_lock_pi() retry path\n\nFuzzying/stressing futexes triggered:\n\n WARNING: kernel/futex/core.c:825 at wait_for_owner_exiting+0x7a/0x80, CPU#11: futex_lock_pi_s/524\n\nWhen futex_lock_pi_atomic() sees the owner is exiting, it returns -EBUSY\nand stores a refcounted task pointer in 'exiting'.\n\nAfter wait_for_owner_exiting() consumes that reference, the local pointer\nis never reset to nil. Upon a retry, if futex_lock_pi_atomic() returns a\ndifferent error, the bogus pointer is passed to wait_for_owner_exiting().\n\n CPU0\t\t\t CPU1\t\t CPU2\n futex_lock_pi(uaddr)\n // acquires the PI futex\n exit()\n futex_cleanup_begin()\n futex_state = EXITING;\n\t\t\t futex_lock_pi(uaddr)\n\t\t\t futex_lock_pi_atomic()\n\t\t\t\t attach_to_pi_owner()\n\t\t\t\t // observes EXITING\n\t\t\t\t *exiting = owner; // takes ref\n\t\t\t\t return -EBUSY\n\t\t\t wait_for_owner_exiting(-EBUSY, owner)\n\t\t\t\t put_task_struct(); // drops ref\n\t\t\t // exiting still points to owner\n\t\t\t goto retry;\n\t\t\t futex_lock_pi_atomic()\n\t\t\t\t lock_pi_update_atomic()\n\t\t\t\t cmpxchg(uaddr)\n\t\t\t\t\t*uaddr ^= WAITERS // whatever\n\t\t\t\t // value changed\n\t\t\t\t return -EAGAIN;\n\t\t\t wait_for_owner_exiting(-EAGAIN, exiting) // stale\n\t\t\t\t WARN_ON_ONCE(exiting)\n\nFix this by resetting upon retry, essentially aligning it with requeue_pi.",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Clear stale exiting pointer in futex_lock_pi() retry path\n\nFuzzying/stressing futexes triggered:\n\n WARNING: kernel/futex/core.c:825 at wait_for_owner_exiting+0x7a/0x80, CPU#11: futex_lock_pi_s/524\n\nWhen futex_lock_pi_atomic() sees the owner is exiting, it returns -EBUSY\nand stores a refcounted task pointer in 'exiting'.\n\nAfter wait_for_owner_exiting() consumes that reference, the local pointer\nis never reset to nil. Upon a retry, if futex_lock_pi_atomic() returns a\ndifferent error, the bogus pointer is passed to wait_for_owner_exiting().\n\n CPU0\t\t\t CPU1\t\t CPU2\n futex_lock_pi(uaddr)\n // acquires the PI futex\n exit()\n futex_cleanup_begin()\n futex_state = EXITING;\n\t\t\t futex_lock_pi(uaddr)\n\t\t\t futex_lock_pi_atomic()\n\t\t\t\t attach_to_pi_owner()\n\t\t\t\t // observes EXITING\n\t\t\t\t *exiting = owner; // takes ref\n\t\t\t\t return -EBUSY\n\t\t\t wait_for_owner_exiting(-EBUSY, owner)\n\t\t\t\t put_task_struct(); // drops ref\n\t\t\t // exiting still points to owner\n\t\t\t goto retry;\n\t\t\t futex_lock_pi_atomic()\n\t\t\t\t lock_pi_update_atomic()\n\t\t\t\t cmpxchg(uaddr)\n\t\t\t\t\t*uaddr ^= WAITERS // whatever\n\t\t\t\t // value changed\n\t\t\t\t return -EAGAIN;\n\t\t\t wait_for_owner_exiting(-EAGAIN, exiting) // stale\n\t\t\t\t WARN_ON_ONCE(exiting)\n\nFix this by resetting upon retry, essentially aligning it with requeue_pi."
}
],
"id": "CVE-2026-31555",
"lastModified": "2026-11-05T22:18:40.093",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 5.5,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 3.6,
"source": "nvd@nist.gov",
"type": "Primary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-31555",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-11-05T21:38:41.447334Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-04-24T15:16:29.837",
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"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Modified",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "NVD-CWE-noinfo"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
},
"severity": "MEDIUM",
"source": "nvd",
"title": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Clear stale exiting pointer in futex_lock..."
}