* [CVE-2026-98058][LOW] bpf: Mark syscall helpers as sleepable [ Upstream
@ 2026-09-25 17:20 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-25 17:20 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98058
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: bpf: Mark syscall helpers as sleepable [ Upstream
Commit: 3408e98f06ce06ea6a58ca6c39da9c23f0029c06
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3408e98f06ce06ea6a58ca6c39da9c23f0029c06
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98058
Analysis date: Fri, 25 Sep 2026 13:20:19 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98058 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98058
The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.
The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.
Published priority for this report: LOW
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-98058 LOW https://www.kernelcve.org/list/?q=CVE-2026-98058 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-667;CWE-703;**CWE-400;BEST CVSS score: '5.5';DESCR 'A BPF syscall program can register a BPF timer callback that runs in hrtimer softirq context while retaining access to bpf_sys_bpf and bpf_sys_close helpers. These helpers can sleep because they may take mutexes allocate memory with GFP_KERNEL or wait for an RCU grace period. Calling them from the atomic callback context can cause a scheduling while atomic failure and may result in a kernel warning BUG or panic. For the CVSS the PR:L because a local user or process must be able to load and operate the affected BPF program type and create a BPF timer. The issue is not network reachable. Impact is denial of service only. The patch context does not provide evidence of memory corruption information disclosure integrity impact or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES BPF SIMPLEFIX IMPROVEONLY LINUS INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Reliable kernel stability failure. A BPF timer callback can call helpers that may sleep from hrtimer softirq context, causing a scheduling while atomic failure. Depending on kernel configuration this can produce a BUG, panic, or serious kernel stability failure.
* No memory-corruption signal awarded. The patch establishes an invalid sleep-in-atomic-context operation, not a UAF, OOB access, use of stale state, refcount misuse, arbitrary write, or type confusion.
* No remote-reachability signal awarded. Triggering requires local BPF program operations and is not reachable through ordinary network traffic.
* No local-unprivileged trigger signal awarded. The supplied patch does not establish that the complete BPF_PROG_TYPE_SYSCALL load, timer setup, and helper invocation sequence is available to an ordinary unprivileged user.
* No host-admin penalty applied. Host-admin-equivalent privilege is not positively established by the supplied patch.
* No BPF high-control bonus awarded. BPF object creation alone does not provide attacker-controlled memory layout, post-free object reuse, or another exploitation-relevant corruption primitive.
* No confidentiality or integrity signal awarded. There is no demonstrated disclosure, unauthorized modification, security-boundary bypass, or privilege-escalation primitive.
* No additional paranoid point awarded. A stronger outcome would rely on the same scheduling-while-atomic failure and would double-count the DoS consequence.
3. Reachability analysis
The triggering actor is a local process that can load and execute a BPF_PROG_TYPE_SYSCALL program, create a BPF timer, and invoke bpf_sys_bpf or bpf_sys_close from the timer callback.
The patch establishes that the verifier previously retained the syscall helper set for a non-sleepable timer callback. It does not show the exact capability checks for loading this program type, creating the timer, or accessing the relevant helpers in the evaluated product. Therefore HostAdminRequired is UNKNOWN rather than YES or NO.
Namespace-scoped reachability is also unresolved. The supplied context does not establish that all required BPF loading and timer operations can be completed with attacker-controlled namespace capabilities. No prior device setup, special hardware, network listener, firmware interaction, or race is required by the described trigger.
4. Primitive and severity interpretation
The exact primitive is an invalid invocation of potentially sleeping helpers from atomic hrtimer softirq context. bpf_sys_bpf can execute syscall operations that take mutexes, allocate with GFP_KERNEL, or wait for RCU. bpf_sys_close can reach close_fd and filp_close, which may sleep.
This is CLASS_C because the demonstrated behavior is scheduling while atomic, warning, BUG, panic, or DoS. It is not a lifetime violation, active structured-object UAF, fixed stale-storage UAF, repeated release, refcount mutation, arbitrary read, arbitrary write, or authorization bypass.
The practical consequence is kernel instability or denial of service when the invalid callback executes. Privilege escalation, confidentiality impact, integrity impact, controlled kernel corruption, and attacker-controlled post-free reuse are speculative and unsupported by the patch. ImportantCandidate is NO because no meaningful corruption or security-boundary primitive remains unresolved. AutoDowngradeAllowed is YES because the issue is a constrained invalid-context DoS condition without an established memory-corruption primitive.
5. One-sentence report phrase
A local BPF syscall program can invoke sleeping helpers from a non-sleepable timer callback, causing a scheduling while atomic failure and potential kernel denial of service.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch demonstrates a verifier context-validation omission that causes an atomic-context sleep failure, but it does not establish memory corruption, a UAF, privilege escalation, information disclosure, or a security-boundary bypass.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: bpf: Mark syscall helpers as sleepable [ Upstream
Commit: 3408e98f06ce06ea6a58ca6c39da9c23f0029c06
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3408e98f06ce06ea6a58ca6c39da9c23f0029c06
Changed files:
kernel/bpf/syscall.c
Diff excerpt:
Not included in this email. See the upstream URL for the full patch.
Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3408e98f06ce06ea6a58ca6c39da9c23f0029c06
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98058 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98058
The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.
The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.
The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.
Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:
Conservative CVSS vector: Not available
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 5.5
The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.
CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.
A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.
Conservative ActionableScore: unknown
Paranoid ActionableScore: 1
The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.
For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:
ActionableScore below 5 -> MODERATE REGULAR
ActionableScore 5 or more -> MODERATE 7.0
The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.
There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).
KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.
AL-KERNEL base severity for this report: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW
These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).
Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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