* [CVE-2026-98046][LOW] bpf: Mark bpf_btf_find_by_name_kind() as sleepable [ Upstream
@ 2026-09-25 13:32 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-25 13:32 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98046
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: bpf: Mark bpf_btf_find_by_name_kind() as sleepable [ Upstream
Commit: 29e40175617216fbd4544529f6bfb51d1ab95ba1
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=29e40175617216fbd4544529f6bfb51d1ab95ba1
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98046
Analysis date: Fri, 25 Sep 2026 09:32:00 -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-2026-98046 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98046
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-2026-98046 LOW https://www.kernelcve.org/list/?q=CVE-2026-98046 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-754;CWE-667;**CWE-400;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A BPF helper can allocate a BTF file descriptor through anon_inode_getfd while executing in a non sleepable context such as a BPF timer callback. The verifier did not mark bpf_btf_find_by_name_kind as sleepable, so the helper can sleep in softirq context and may install the new file descriptor into the interrupted task. This can cause atomic context warnings, kernel instability, or resource exhaustion through repeated callback execution. For the CVSS the PR:L is used because an attacker needs local access to the BPF interface and the ability to load or use a suitable BPF program. The issue is not network reachable. The base impact is limited availability impact. The paranoid score allows high availability impact from sustained invalid callback execution but does not claim confidentiality or integrity impact because no memory corruption, information leak, or arbitrary write primitive is demonstrated. YES REQUIRES MANUAL CHECK.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) YES BPF SIMPLEFIX LINUS NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
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 Availability impact realistic. The helper can repeatedly allocate BTF file descriptors while executing in a softirq context and install them into interrupted tasks. This can consume file descriptor table capacity and cause local process failures or resource pressure.
* +0 Invalid atomic context execution. Sleeping through anon_inode_getfd in a BPF timer softirq context is invalid and may generate scheduling while atomic warnings or other kernel diagnostics. The supplied patch does not establish a reliable kernel crash or panic.
* +0 No concrete persistent kernel reference leak awarded. The unwanted file descriptor remains associated with the interrupted task and is expected to be closed during normal task exit.
* +0 No Real UAF, stale pointer, double release, refcount mutation, OOB access, arbitrary write, or controlled object replacement is established.
* +0 No confidentiality or integrity signal awarded. Installing a BTF fd in an interrupted task is an unintended cross-task resource side effect, but supplied evidence does not show disclosure, unauthorized protected-resource access, or modification of protected state.
* +0 No remote reachability awarded. The affected path requires local BPF program execution.
* +0 No local unprivileged trigger awarded. The complete ability to load a suitable BPF program, create a BPF timer, and invoke this helper is not established below host-admin-equivalent privilege.
* +0 No privilege penalty applied. The complete privilege boundary is unresolved, and UNKNOWN privilege must not be treated as proven host-admin-only access.
* +0 No BPF cleanup UAF floor applies. This is not a UAF or lifetime-corruption issue.
3. Reachability analysis
The triggering actor is a local process that can load or use a BPF program containing bpf_btf_find_by_name_kind and execute it through a non-sleepable context such as a BPF timer callback.
The supplied material establishes that the verifier previously allowed this helper in timer callbacks, but it does not establish the full privilege model for the affected product. In common hardened configurations, loading the relevant BPF program may require CAP_BPF, CAP_SYS_ADMIN, or other privileged BPF access. Therefore HostAdminRequired is UNKNOWN rather than YES or NO.
NamespaceScopedPrivilege is also UNKNOWN. The supplied patch does not show that the complete sequence of BPF load, timer creation, BTF lookup, and callback execution can be performed using only an attacker-created user or network namespace. No network, device, boot, firmware, or special hardware prerequisite is established.
This is not a timing race. A loaded eligible BPF timer program can repeatedly execute the problematic helper, but the practical severity depends on BPF access policy and on which tasks are interrupted when the timer callback runs.
4. Primitive and severity interpretation
The established primitive is an invalid execution-context and cross-task file descriptor installation issue. bpf_btf_find_by_name_kind can reach anon_inode_getfd, which may sleep and allocates an fd in the current task. In a timer callback, current can be the task interrupted by softirq processing rather than the BPF program loader.
This is not an active structured-object UAF, fixed stale storage UAF, double-free, repeated release, refcount mutation, memory corruption, or authorization ALLOW-versus-DENY bypass. The demonstrated consequence is invalid sleep in softirq context and possible unintended file descriptor accumulation in interrupted tasks.
The speculative consequence is broader local availability degradation if repeated timer execution fills file descriptor tables or triggers severe atomic-context diagnostics. A host-wide crash, privilege escalation, protected resource theft, controlled corruption, or information disclosure is not established by the supplied evidence.
PrimitiveClass is CLASS_C because the demonstrated behavior is invalid-state and DoS-like behavior without an independently useful corruption primitive. ImportantCandidate is NO because no meaningful exploitation leverage beyond resource consumption and invalid-context execution is established. AutoDowngradeAllowed is YES because no unresolved Class A or meaningful Class B lifetime/corruption primitive exists.
Likely operational severity is Low to ordinary Moderate. Manual review remains useful to verify product-specific BPF privilege policy and whether the affected BPF helper is available to delegated or container-scoped BPF users.
5. One-sentence report phrase
A BPF helper could sleep while running in a non-sleepable timer callback and install a BTF file descriptor into an interrupted task, causing invalid softirq-context behavior and possible local resource exhaustion.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Review BPF loader permissions, delegated CAP_BPF usage, unprivileged BPF policy, BPF timer availability, and whether repeated unintended fd installation can materially affect long-running victim processes.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: bpf: Mark bpf_btf_find_by_name_kind() as sleepable [ Upstream
Commit: 29e40175617216fbd4544529f6bfb51d1ab95ba1
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=29e40175617216fbd4544529f6bfb51d1ab95ba1
Changed files:
kernel/bpf/btf.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=29e40175617216fbd4544529f6bfb51d1ab95ba1
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98046 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98046
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: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
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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