* [CVE-2026-98413][LOW] selinux: always fill AVC decision in avc_has_perm_noaudit()
@ 2026-10-15 3:00 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-15 3:00 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98413
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: selinux: always fill AVC decision in avc_has_perm_noaudit()
Commit: c781e737aa0de95289b1774d5fd29388895737a9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c781e737aa0de95289b1774d5fd29388895737a9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98413
Analysis date: Wed, 14 Oct 2026 23:00:50 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
An empty SELinux permission request could propagate an uninitialized AVC decision into audit and per-task cache processing, but the affected branch still denies access and no concrete authorization bypass, disclosure, or kernel corruption is established.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98413 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98413
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-2026-98413 LOW https://www.kernelcve.org/list/?q=CVE-2026-98413 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=LOW RESULT=DIFF TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (independent Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L';*CWE-457;CWE-908;CWE-665;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N';BEST CVSS score: '4.5';DESCR 'avc_has_perm_noaudit can return EACCES for an empty requested permission set without initializing the caller supplied av_decision. Callers then pass this undefined decision to avc_audit, and an inode hook may store it in a per task decision cache. The demonstrated primitive is an uninitialized stack read and propagation of undefined security decision metadata, not a UAF, OOB access, or arbitrary write. This can make SELinux auditing or cached decision behavior inconsistent. A direct policy bypass or disclosure is not proven, but limited confidentiality and integrity impact remains plausible because the undefined value reaches security decision consumers. For the CVSS the PR:L value is used for the paranoid score because a local user or process is needed to reach the SELinux hook path, while reliable control of the empty request and stack contents is not established. The issue is not network reachable by itself. Impact is primarily incorrect audit or decision state, with no demonstrated kernel crash. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.5 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS 2.5 and ActionableScore 1 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE WARNONLY SIMPLEFIX LINUS KPANIC_UNSUPPORTED_REMOVED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
## 1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::
## 2. Signal breakdown
Positive signals:
* +1 Weak or indirect invalid-state primitive. An uninitialized stack `av_decision` is consumed by `avc_audit()` and may be stored in the per-task decision cache.
Negative signals:
* None applied. Trigger privilege, namespace scope, and exact caller reachability are unresolved, so no speculative privilege or rarity penalty is used.
Important non-awarded signals:
* No UAF, OOB access, heap overwrite, arbitrary write, or lifetime violation is established.
* No DENY-to-ALLOW authorization change is established. The vulnerable branch still returns `-EACCES`.
* No confidentiality or integrity point is awarded because no protected data disclosure or unauthorized modification is demonstrated.
* No crash point is awarded because the commit demonstrates a warning and undefined decision metadata, not a kernel panic.
* No central authorization-helper fan-out point is awarded because no caller is shown receiving an incorrect successful authorization.
* B4-PENDING does not apply because below-host-admin reachability, a protected resource, and an actual authorization bypass are not established.
* B5-R and B3-PENDING do not apply because there is no OOB write or shared-backing write.
## 3. Reachability analysis
A process may enter SELinux hooks, but the supplied evidence does not show that an ordinary user can reliably force `avc_has_perm_noaudit()` to receive an empty `requested` mask. The complete trigger may depend on an unusual internal caller state rather than direct attacker control.
No host-UID-0 requirement, host-admin requirement, namespace-scoped capability path, prior privileged setup, special hardware, or direct network trigger is established. There is no race.
## 4. Primitive and severity interpretation
The exact primitive is an uninitialized stack read followed by propagation of undefined `struct av_decision` fields into audit processing and an inode per-task cache. This is invalid security-state consumption, not memory corruption in the write or lifetime sense.
The function returns `-EACCES`, so the patch does not directly establish an SELinux permission bypass. Undefined audit selection or cache behavior is possible, but no reachable protected-resource access, disclosure, persistent policy modification, crash, or privilege escalation is demonstrated.
This is therefore CLASS_C rather than CLASS_A or CLASS_B. ImportantCandidate is NO because there is no concrete authorization bypass or exploitable corruption primitive. AutoDowngradeAllowed is YES, although targeted review is recommended because undefined data reaches SELinux audit and cache consumers.
## 5. One-sentence report phrase
An empty SELinux permission request could propagate an uninitialized AVC decision into audit and per-task cache processing, but the affected branch still denies access and no concrete authorization bypass, disclosure, or kernel corruption is established.
## 6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Review the inode cache consumer and all empty-request call paths to confirm that undefined decision fields cannot influence a later permission decision, but current evidence does not require Important-class preservation.
## 7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: selinux: always fill AVC decision in avc_has_perm_noaudit()
Commit: c781e737aa0de95289b1774d5fd29388895737a9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c781e737aa0de95289b1774d5fd29388895737a9
Commit description:
avc_has_perm_noaudit() is documented to return a copy of the access
decision in @avd , but its early return for an empty requested permission
set leaves the buffer untouched. All callers pass an uninitialized
stack variable and afterwards feed it to avc_audit(), and the inode hook
even stores it in the per-task decision cache.
Fill in a deny-all, audit-all decision, similar to avd_init(), so every
caller receives a defined value at no cost on the hot path.
Cc: [email protected]
Fixes: e6f2f38 ("selinux: replace BUG_ONs with WARN_ONs in avc.c")
Signed-off-by: Christian Göttsche <[email protected]>
Reviewed-by: Stephen Smalley <[email protected]>
Signed-off-by: Paul Moore <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
security/selinux/avc.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=c781e737aa0de95289b1774d5fd29388895737a9
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98413 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98413
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:H/PR:L/UI:N/S:U/C:N/I:L/A:N
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L
The Best / paranoid CVSS score: 4.5
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).
^ permalink raw reply [relevance 21%]
Results 1-1 of 1 | reverse | sort options + mbox downloads above
-- links below jump to the message on this page --
2026-10-15 3:00 21% [CVE-2026-98413][LOW] selinux: always fill AVC decision in avc_has_perm_noaudit() AL-KERNEL
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox