Unknown

CVE-2026-98861 — fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching()

In the Linux kernel, the following vulnerability has been resolved: fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching() unregister_fprobe() and unregister_fprobe_async() (used by BPF kprobe-multi) rely on standard RCU grace periods (synchronize_rcu() and call_rcu()) to wait until in-flight fprobe handlers complete before freeing the fprobe. However, if an fprobe handler executes while RCU is not watching (such as in the idle loop or nohz_full extended quiescent states), standard RCU does not track preemption-disabled sections. Consequently, synchronize_rcu() does not wait for those executions, which can lead to a use-after-free if the fprobe is freed immediately after unregistration. Ensure handlers exit early when !rcu_is_watching(). Furthermore, fprobe_fgraph_entry() and fprobe_ftrace_entry() previously used guard(rcu)() and rcu_read_lock(), which invoke lockdep on every hit under CONFIG_PROVE_LOCKING. This adds overhead and can cause lockdep recursion if probed functions interact with lockdep. Since rhltable_lookup() and rhl_for_each_entry_rcu() use rcu_dereference_all_check() (which checks rcu_read_lock_any_held()), holding preemption disabled via rcu_read_lock_sched_notrace() is fully valid and sufficient so long as rcu_is_watching() is true. Define and use guard(rcu_sched_notrace)() across fprobe_ftrace_entry(), fprobe_fgraph_entry(), and fprobe_return(). This eliminates fast-path rcu_read_lock() and lockdep overhead while guaranteeing safe grace period synchronization.

Published Oct 18, 2026 · Updated Oct 18, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

No scoring signals.

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 56b4cfcf1518245493c60fd39c56978f508f1816 and < a85d0f00671b4d4527317c10ba018680f7d8d673≥ 657b594b2084b39a4bc6d8493aa2140cb00cea49 and < dd4a0d4993633b45470abf6da4ea0ca563402245≥ 657b594b2084b39a4bc6d8493aa2140cb00cea49 and < e0a6249190402a28f1e2925a81acf573157d55efversion a4f6a9005ed6cfd360ef2520430927f05f92ffb0≥ 6.18.34 and < 6.18.56≥ 7.0.11 and < 7.1version 7.1	Vulnerable	CVE Program (cve.org) e CISA ADP

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 18, 2026
Affected products added · linux/linux
Oct 18, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Received
Oct 18, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 18, 2026 · NIST National Vulnerability Database
CVE published
Oct 18, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 18, 2026 – Oct 18, 2026

References

3 on the record

git.kernel.org/stable/c/e0a6249190402a28f1e2925a81acf573157d55ef
NIST National Vulnerability Database
git.kernel.org/stable/c/a85d0f00671b4d4527317c10ba018680f7d8d673
NIST National Vulnerability Database
git.kernel.org/stable/c/dd4a0d4993633b45470abf6da4ea0ca563402245
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Unknown CVE-2026-98866 sched/cache: Introduce task_struct->sched_cache_grp to fix UAF 17h
Unknown CVE-2026-98867 dm-pcache: bound the logical key offset from persistent memory 17h
Unknown CVE-2026-98868 dm-pcache: reject a kset that overruns its segment 17h
Unknown CVE-2026-98856 kprobes: Skip disarmed probes when checking optkprobe overlap 17h
Unknown CVE-2026-98857 ipvs: bound LBLCR and LBLC cache growth 17h
Unknown CVE-2026-98858 io_uring: fix task_work add use-after-free with SQPOLL 17h

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No FIRST EPSS score.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-98861 is "fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching()", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

Comments

Moderated technical discussion. Read the community guidelines.

No comments yet.