CVE-2026-98260 - Vulnerability Details

- exec: Cleanup POSIX timers right after de_thread()

Description

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() ]

Published: 2026-10-06

Score: 7.8 High

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

In the Linux kernel, a use‑after‑free occurs when a non‑leader thread arms a POSIX thread CPU timer and then performs an execve that fails before the timer cleanup runs. The timer’s node remains queued in the task’s timer list while the underlying timer structure is freed, which can corrupt kernel memory or crash the system. This results in a potential denial‑of‑service or data corruption attack.

Affected Systems

All Linux kernel builds that do not include the commit that moves the POSIX timer cleanup immediately after de_thread(). The affected identifier corresponds to all versions of the Linux kernel; repositories show the fix applied in commits such as 6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce and its subsequent stable branches.

Risk and Exploitability

The CVSS score of 7.8 indicates a high severity flaw. The EPSS score of less than 1 % suggests a very low likelihood of exploitation. The vulnerability is not listed in CISA’s KEV catalog. Exploitation requires local code that arranges a CLOCK_THREAD_CPUTIME_ID timer on a thread that then executes a failing execve; no public exploitation has been reported.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59`	affected	< f6c93e8ecaaf12959b7ef6eb611351001db2ff5d
`55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59`	affected	< 6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce
`55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59`	affected	< d9ae467e617ca29b825493a362bf0d75ad5f4ac3
`55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59`	affected	< 75aa08b93c65766040f9ca99f41ac85ad22596b6
`55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59`	affected	< d602877baf36c43c788a5f472c977e0be414029f
`55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59`	affected	< acb03d3881818581052924a9bbbe92b8741ed448

Linux

affected

Version	Status	Constraints
`5.7`	affected	—
`0`	unaffected	< 5.7
`6.1.191`	unaffected	≤ 6.1.*
`6.6.158`	unaffected	≤ 6.6.*
`6.12.112`	unaffected	≤ 6.12.*
`6.18.54`	unaffected	≤ 6.18.*
`7.2.8`	unaffected	≤ 7.2.*
`7.3`	unaffected	≤ *

No data.

Vendor Product Confidence Versions

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59,6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce)`	affected	code_commit	—
`[55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59,d9ae467e617ca29b825493a362bf0d75ad5f4ac3)`	affected	code_commit	—
`[55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59,75aa08b93c65766040f9ca99f41ac85ad22596b6)`	affected	code_commit	—
`[55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59,d602877baf36c43c788a5f472c977e0be414029f)`	affected	code_commit	—
`[55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59,acb03d3881818581052924a9bbbe92b8741ed448)`	affected	code_commit	—

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`5.7`	affected	semver	—
`[0,5.7)`	unaffected	semver	—
`[6.6.158,6.7.0)`	unaffected	semver	—
`[6.12.112,6.13.0)`	unaffected	semver	—
`[6.18.54,6.19.0)`	unaffected	semver	—
`[7.2.8,7.3.0)`	unaffected	semver	—
`[7.3-rc4,*]`	unaffected	generic	—

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Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Update the kernel to a version that includes the fix implemented by commit 6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce; the stable branch contains the patch.
If a kernel upgrade is not immediately possible, audit applications that create CLOCK_THREAD_CPUTIME_ID timers to ensure timers are disarmed or deleted before invoking execve, thereby preventing the timer node from remaining queued when the task exits.
As a temporary mitigation, consider disabling POSIX timers at kernel configuration time (remove CONFIG_POSIX_TIMERS) or applying a boot parameter that limits timer usage; additionally, monitor system logs for use‑after‑free errors or abnormal crashes.

Generated by OpenCVE AI on October 11, 2026 at 06:29 UTC.

Tracking

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Advisories

Source	ID	Title
Debian DLA	DLA-4841-1	linux security update
Debian DLA	DLA-4850-1	linux-6.12 security update
Debian DSA	DSA-6568-1	linux security update

No CVSS v4.0

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00184.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98260.mbox
https://git.kernel.org/stable/c/6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce
https://git.kernel.org/stable/c/75aa08b93c65766040f9ca99f41ac85ad22596b6
https://git.kernel.org/stable/c/acb03d3881818581052924a9bbbe92b8741ed448
https://git.kernel.org/stable/c/d602877baf36c43c788a5f472c977e0be414029f
https://git.kernel.org/stable/c/d9ae467e617ca29b825493a362bf0d75ad5f4ac3
https://git.kernel.org/stable/c/f6c93e8ecaaf12959b7ef6eb611351001db2ff5d
https://nvd.nist.gov/vuln/detail/CVE-2026-98260
https://www.cve.org/CVERecord?id=CVE-2026-98260

History

Fri, 30 Oct 2026 12:45:00 +0000

Type	Values Removed	Values Added
References		https://git.kernel.org/stable/c/f6c93e8ecaaf12959b7ef6eb611351001db2ff5d

Sun, 11 Oct 2026 05:30:00 +0000

Type	Values Removed	Values Added
Weaknesses	CWE-416

Sun, 11 Oct 2026 00:30:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-825
References		https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98260.mbox https://nvd.nist.gov/vuln/detail/CVE-2026-98260 https://www.cve.org/CVERecord?id=CVE-2026-98260
Metrics	threat_severity `None`	threat_severity `Moderate`

Wed, 07 Oct 2026 12:30:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-416

Wed, 07 Oct 2026 10:00:00 +0000

Type	Values Removed	Values Added
Weaknesses	CWE-416

Wed, 07 Oct 2026 07:00:00 +0000

Type	Values Removed	Values Added
Metrics		cvssV3_1 `{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}`

Tue, 06 Oct 2026 14:30:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-416

Tue, 06 Oct 2026 09:00:00 +0000

Type	Values Removed	Values Added
Description		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() ]
Title		exec: Cleanup POSIX timers right after de_thread()
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce https://git.kernel.org/stable/c/75aa08b93c65766040f9ca99f41ac85ad22596b6 https://git.kernel.org/stable/c/acb03d3881818581052924a9bbbe92b8741ed448 https://git.kernel.org/stable/c/d602877baf36c43c788a5f472c977e0be414029f https://git.kernel.org/stable/c/d9ae467e617ca29b825493a362bf0d75ad5f4ac3

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-10-06T08:45:24.711Z

Updated: 2026-10-30T12:37:58.294Z

Reserved: 2026-09-25T10:25:14.332Z

Link: CVE-2026-98260

Vulnrichment

No data.

NVD

Status : Received

Published: 2026-10-06T09:18:15.040

Modified: 2026-10-30T13:21:12.320

Link: CVE-2026-98260

Redhat

Severity : Moderate

Publid Date: 2026-10-06T00:00:00Z

Links: CVE-2026-98260 - Bugzilla

OpenCVE Enrichment

Updated: 2026-10-11T06:30:13Z

Weaknesses

CWE-825
Expired Pointer Dereference

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

Subscriptions

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