CVE-2026-98260 (GCVE-0-2026-98260)
Vulnerability from cvelistv5 – Published: 2026-10-06 08:45 – Updated: 2026-10-07 06:49
VLAI
EPSS
VEX
Title
exec: Cleanup POSIX timers right after de_thread()
Summary
In the Linux kernel, the following vulnerability has been resolved:
exec: Cleanup POSIX timers right after de_thread()
A per-thread CPU timer holds a reference to the PID of the thread it is
attached to and, while it is armed, its node is queued in that thread's
posix_cputimers. The task is looked up by that PID.
When a non-leader thread exec()s, de_thread() changes which task owns
that PID. pid_task(timer->it.cpu.pid, PIDTYPE_PID) then returns NULL,
but the node is still queued on tsk, which is alive. timer_lock_sighand()
takes a failed lookup to mean that the node is already dequeued, so it
has nothing to undo.
begin_new_exec() calls posix_cpu_timers_exit(me) right after
exec_task_namespaces() and that removes the leftover node, so the state
normally stays invisible. But bprm->point_of_no_return is set before
de_thread(), so if unshare_files(), set_mm_exe_file(), exec_mmap() or
exec_task_namespaces() fails, the task dies before it gets there.
exit_itimers() then frees the k_itimer while its node is still queued,
and reaping tsk later erases that freed node from the rbtree.
In short:
the non-leader thread B the parent
timer_create(CLOCK_THREAD_CPUTIME_ID)
timer_settime()
arm_timer() // the node is queued on B
execve()
de_thread(B)
exchange_tids(B, leader) // B's PID now belongs to the leader
release_task(leader)
__exit_signal(leader)
posix_cpu_timers_exit(leader) // cleans leader's queue, not B's
__unhash_process(leader) // that PID has no task anymore
exec_mmap()
mmap_read_lock_killable(old_mm)
kill(B, SIGKILL)
// -EINTR
get_signal()
do_exit()
exit_itimers()
posix_timer_delete()
posix_cpu_timer_del()
posix_timer_unhash_and_free() // freed while still queued
wait4()
release_task(B)
posix_cpu_timers_exit(B)
cleanup_timerqueue()
timerqueue_del() // use-after-free
Move the POSIX timer cleanup right after de_thread() before any of the
later failure conditions brings the task into do_exit().
[ tglx: Move the cleanup right after de_thread() ]
Severity
7.8 (High)
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | |
|---|---|---|---|
| Linux | Linux |
Affected:
55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < 6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce
(git)
Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < d9ae467e617ca29b825493a362bf0d75ad5f4ac3 (git) Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < 75aa08b93c65766040f9ca99f41ac85ad22596b6 (git) Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < d602877baf36c43c788a5f472c977e0be414029f (git) Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < acb03d3881818581052924a9bbbe92b8741ed448 (git) |
|
| Linux | Linux |
Affected:
5.7
Unaffected: 0 , < 5.7 (semver) Unaffected: 6.6.158 , ≤ 6.6.* (semver) Unaffected: 6.12.112 , ≤ 6.12.* (semver) Unaffected: 6.18.54 , ≤ 6.18.* (semver) Unaffected: 7.2.8 , ≤ 7.2.* (semver) Unaffected: 7.3-rc4 , ≤ * (original_commit_for_fix) |
{
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"product": "Linux",
"programFiles": [
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],
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{
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"status": "unaffected",
"version": "7.2.8",
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{
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nexec: Cleanup POSIX timers right after de_thread()\n\nA per-thread CPU timer holds a reference to the PID of the thread it is\nattached to and, while it is armed, its node is queued in that thread\u0027s\nposix_cputimers. The task is looked up by that PID.\n\nWhen a non-leader thread exec()s, de_thread() changes which task owns\nthat PID. pid_task(timer-\u003eit.cpu.pid, PIDTYPE_PID) then returns NULL,\nbut the node is still queued on tsk, which is alive. timer_lock_sighand()\ntakes a failed lookup to mean that the node is already dequeued, so it\nhas nothing to undo.\n\nbegin_new_exec() calls posix_cpu_timers_exit(me) right after\nexec_task_namespaces() and that removes the leftover node, so the state\nnormally stays invisible. But bprm-\u003epoint_of_no_return is set before\nde_thread(), so if unshare_files(), set_mm_exe_file(), exec_mmap() or\nexec_task_namespaces() fails, the task dies before it gets there.\nexit_itimers() then frees the k_itimer while its node is still queued,\nand reaping tsk later erases that freed node from the rbtree.\n\nIn short:\n\n the non-leader thread B the parent\n\n timer_create(CLOCK_THREAD_CPUTIME_ID)\n timer_settime()\n arm_timer() // the node is queued on B\n execve()\n de_thread(B)\n exchange_tids(B, leader) // B\u0027s PID now belongs to the leader\n release_task(leader)\n __exit_signal(leader)\n posix_cpu_timers_exit(leader) // cleans leader\u0027s queue, not B\u0027s\n __unhash_process(leader) // that PID has no task anymore\n exec_mmap()\n mmap_read_lock_killable(old_mm)\n kill(B, SIGKILL)\n // -EINTR\n get_signal()\n do_exit()\n exit_itimers()\n posix_timer_delete()\n posix_cpu_timer_del()\n posix_timer_unhash_and_free() // freed while still queued\n wait4()\n release_task(B)\n posix_cpu_timers_exit(B)\n cleanup_timerqueue()\n timerqueue_del() // use-after-free\n\nMove the POSIX timer cleanup right after de_thread() before any of the\nlater failure conditions brings the task into do_exit().\n\n[ tglx: Move the cleanup right after de_thread() ]"
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The bug needs local syscalls: timer_create(CLOCK_THREAD_CPUTIME_ID) and timer_settime() on a non-leader thread, then execve(). That thread\u0027s exec must fail after de_thread() in begin_new_exec() (e.g. exec_mmap() returning -EINTR on SIGKILL). No remote protocol carries any of this input.\nAC:L - The attacker controls both sides of the race. Their own parent sends SIGKILL while exec_mmap() waits on down_write_killable(exec_update_lock) or mmap_read_lock_killable(old_mm), and they can create that lock contention with their own CLONE_VM or /proc readers. No condition outside their control is needed.\nPR:L - Arming a thread CPU timer, calling execve and signalling one\u0027s own child are all available to any unprivileged user, with no capability checks on this path. A local unprivileged account is enough.\nUI:N - The attacker\u0027s own processes perform every step (timer arm, execve from a non-leader thread, SIGKILL, wait4 reap), so no victim action is needed.\nS:U - The memory corruption is inside the kernel that the attacker\u0027s process runs on. The outcome is a normal local privilege escalation, with no VM or sandbox boundary crossed.\nC:H - exit_itimers() frees the k_itimer while its cpu_timer node is still linked in the task\u0027s posix_cputimers rbtree. The freed slab object can be reclaimed with attacker-sprayed data, giving a use-after-free that can be turned into kernel memory disclosure.\nI:H - When release_task() reaps the task, posix_cpu_timers_exit() -\u003e cleanup_timerqueue() -\u003e timerqueue_del() calls rb_erase on the freed node and rewrites rbtree pointers in reclaimed memory. That is a use-after-free write which can be used for privilege escalation.\nA:H - The rbtree erase on freed memory corrupts kernel data and can oops or panic the kernel. Any unprivileged user can repeat it at will."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-07T06:49:47.661Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
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"url": "https://git.kernel.org/stable/c/6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce"
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{
"url": "https://git.kernel.org/stable/c/d9ae467e617ca29b825493a362bf0d75ad5f4ac3"
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"url": "https://git.kernel.org/stable/c/75aa08b93c65766040f9ca99f41ac85ad22596b6"
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},
{
"url": "https://git.kernel.org/stable/c/acb03d3881818581052924a9bbbe92b8741ed448"
}
],
"title": "exec: Cleanup POSIX timers right after de_thread()",
"x_generator": {
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"assignerShortName": "Linux",
"cveId": "CVE-2026-98260",
"datePublished": "2026-10-06T08:45:24.711Z",
"dateReserved": "2026-09-25T10:25:14.332Z",
"dateUpdated": "2026-10-07T06:49:47.661Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-98260",
"date": "2026-10-18",
"epss": "0.00134",
"percentile": "0.026"
},
"microsoft_vex": {
"current_release_date": "2026-10-15T02:52:35.000Z",
"cve": "CVE-2026-98260",
"id": "msrc_CVE-2026-98260",
"initial_release_date": "2026-10-07T01:12:00.000Z",
"product_status:fixed": "1",
"product_status:known_affected": "1",
"source": "Microsoft CSAF VEX",
"status": "final",
"title": "exec: Cleanup POSIX timers right after de_thread()",
"url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-98260.json",
"version": "3"
},
"nvd": {
"cve": {
"affected": [
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"product": "Linux",
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"vendor": "Linux",
"versions": [
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"versionType": "semver"
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{
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"version": "6.18.54",
"versionType": "semver"
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"status": "unaffected",
"version": "7.2.8",
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nexec: Cleanup POSIX timers right after de_thread()\n\nA per-thread CPU timer holds a reference to the PID of the thread it is\nattached to and, while it is armed, its node is queued in that thread\u0027s\nposix_cputimers. The task is looked up by that PID.\n\nWhen a non-leader thread exec()s, de_thread() changes which task owns\nthat PID. pid_task(timer-\u003eit.cpu.pid, PIDTYPE_PID) then returns NULL,\nbut the node is still queued on tsk, which is alive. timer_lock_sighand()\ntakes a failed lookup to mean that the node is already dequeued, so it\nhas nothing to undo.\n\nbegin_new_exec() calls posix_cpu_timers_exit(me) right after\nexec_task_namespaces() and that removes the leftover node, so the state\nnormally stays invisible. But bprm-\u003epoint_of_no_return is set before\nde_thread(), so if unshare_files(), set_mm_exe_file(), exec_mmap() or\nexec_task_namespaces() fails, the task dies before it gets there.\nexit_itimers() then frees the k_itimer while its node is still queued,\nand reaping tsk later erases that freed node from the rbtree.\n\nIn short:\n\n the non-leader thread B the parent\n\n timer_create(CLOCK_THREAD_CPUTIME_ID)\n timer_settime()\n arm_timer() // the node is queued on B\n execve()\n de_thread(B)\n exchange_tids(B, leader) // B\u0027s PID now belongs to the leader\n release_task(leader)\n __exit_signal(leader)\n posix_cpu_timers_exit(leader) // cleans leader\u0027s queue, not B\u0027s\n __unhash_process(leader) // that PID has no task anymore\n exec_mmap()\n mmap_read_lock_killable(old_mm)\n kill(B, SIGKILL)\n // -EINTR\n get_signal()\n do_exit()\n exit_itimers()\n posix_timer_delete()\n posix_cpu_timer_del()\n posix_timer_unhash_and_free() // freed while still queued\n wait4()\n release_task(B)\n posix_cpu_timers_exit(B)\n cleanup_timerqueue()\n timerqueue_del() // use-after-free\n\nMove the POSIX timer cleanup right after de_thread() before any of the\nlater failure conditions brings the task into do_exit().\n\n[ tglx: Move the cleanup right after de_thread() ]"
}
],
"id": "CVE-2026-98260",
"lastModified": "2026-10-07T07:17:07.260",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
]
},
"published": "2026-10-06T09:18:15.040",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/75aa08b93c65766040f9ca99f41ac85ad22596b6"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/acb03d3881818581052924a9bbbe92b8741ed448"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/d602877baf36c43c788a5f472c977e0be414029f"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/d9ae467e617ca29b825493a362bf0d75ad5f4ac3"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
},
"redhat_vex": {
"aggregate_severity": "Important",
"current_release_date": "2026-10-16T22:48:51+00:00",
"cve": "CVE-2026-98260",
"id": "CVE-2026-98260",
"initial_release_date": "2026-10-06T00:00:00+00:00",
"product_status:fixed": "1046",
"product_status:known_affected": "185",
"product_status:known_not_affected": "90",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: exec: Cleanup POSIX timers right after de_thread()",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98260.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "moderate",
"current_release_date": "2026-10-07T16:28:17Z",
"cve": "CVE-2026-98260",
"id": "CVE-2026-98260",
"initial_release_date": "2026-10-07T16:28:17Z",
"product_status:known_affected": "341",
"product_status:known_not_affected": "6",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-98260",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-98260.json",
"version": "2"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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