* [CVE-2026-99224][MODERATE 7.0] keys: Protect the type name while describing a key
@ 2026-11-03 2:03 21% AL-KERNEL
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From: AL-KERNEL @ 2026-11-03 2:03 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99224
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: keys: Protect the type name while describing a key
Commit: 19c4de819e52b7f606468fbfe4fcef4e812e2777
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=19c4de819e52b7f606468fbfe4fcef4e812e2777
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99224
Analysis date: Mon, 02 Nov 2026 22:03:57 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
A low-privilege key description request can race privileged key-type retirement and read a freed module-owned type-name string, causing a kernel Oops.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99224 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99224
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: MODERATE 7.0
Manual review required: YES
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-99224 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99224 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both 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:N/A:H';*CWE-416;CWE-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '5.3';DESCR 'A race in keyctl_describe_key can leave kasprintf using a saved key type name pointer after the module that owns the type and string has been unloaded. This is a concrete use after free read that can fault in string and cause a kernel oops or panic. It may also expose limited stale kernel data if the released storage remains readable and its contents are returned by KEYCTL_DESCRIBE, but there is no supported write primitive or privilege escalation path. For the CVSS the PR:L value is used in the paranoid vector because a local user with View permission can execute KEYCTL_DESCRIBE while a privileged module unload supplies the retirement event. The base vector uses PR:H because reliable self triggering normally requires control of module unload. AC:H reflects the required overlap between the two formatting passes and key type retirement. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the manual review requirement was applied. ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold rule was applied. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. 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 INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 1.5 and ActionableScore 0 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) MAYBE LEAK LINUS INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=3
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 3.
* Conservative score: 3; no floor or cap applied.
* Raw paranoid score: 3.
* Paranoid score: 3; no additional supported primitive.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +2 real UAF: `kasprintf()` retains `key->type->name` across allocation; module unload can free the module-owned string before the formatter’s second pass reads it.
* +1 reliable kernel crash/strong DoS: the supplied Oops shows `string()` faulting on the released pointer.
* +1 local low-privilege partial trigger: a task with View permission can invoke `KEYCTL_DESCRIBE`.
* -1 hard timing: exploitation requires overlap between the two formatting passes and privileged key-type/module retirement.
Not awarded:
* No disclosure point: stale bytes being returned is only conditional speculation; no readable-reuse disclosure is demonstrated.
* No structured stale-object leverage: the stale use reads a fixed module-owned name string, not attacker-shaped active fields, callbacks, pointers, or lifetime metadata.
* No arbitrary write, controlled reclaim, repeated release, integrity impact, or LPE is shown.
* No extra availability point; it would duplicate the same Oops/panic consequence.
* B5-R, B3-PENDING, and B4-PENDING do not apply: there is no OOB write, shared-backing write, or DENY-to-ALLOW authorization change.
3. Reachability analysis
A user holding View permission controls the describe operation, but module unload and `unregister_key_type()` are privileged operations controlled by a separate host actor. The supplied evidence does not show that the low-privilege caller can induce unload, nor that one attacker must hold numeric host UID 0. Thus the complete trigger is compound and effective host-admin necessity is unresolved. No namespace-scoped complete trigger is established. The race requires a specific allocation-window overlap, although allocation pressure may enlarge it.
4. Primitive and severity reading
This is a concrete read-side UAF against fixed released module storage. The shown stale operation is `%s` traversal of the freed type-name string, with a demonstrated kernel fault. It is CLASS_B because lifetime protection is genuinely missing, but the patch supports only a constrained stale read—not active-object replacement, post-free mutation, or an independently useful corruption primitive. Important-grade leverage is therefore not shown, and automatic Moderate handling remains permissible after review.
5. One-sentence report phrase
A low-privilege key description request can race privileged key-type retirement and read a freed module-owned type-name string, causing a kernel Oops.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm product-specific module-unload exposure and whether stale mapped module storage can be returned to userspace rather than faulting.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: keys: Protect the type name while describing a key
Commit: 19c4de819e52b7f606468fbfe4fcef4e812e2777
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=19c4de819e52b7f606468fbfe4fcef4e812e2777
Commit description:
keyctl_describe_key() must keep the key type's name alive until
kasprintf() has consumed it. The retained key reference keeps the key
and its description alive, but does not pin the module providing its
type. The name is passed to kasprintf() without holding key->sem.
kvasprintf() uses the saved name pointer in two formatting passes, with
a GFP_KERNEL allocation between them. With AF_RXRPC=m, a task that
passes View permission before type retirement can overlap a privileged
module unload in this order:
1. KEYCTL_DESCRIBE looks up the key, saves key->type->name in the
kasprintf() arguments and completes the first formatting pass.
2. While the formatter is delayed before its second pass,
af_rxrpc_exit() calls unregister_key_type(), which removes the type
from the registry and waits for key_gc_keytype().
3. The collector takes key->sem for writing, retypes the retained key
to key_type_dead and completes retirement. Unregistration and module
exit return, allowing free_module() to release the type and name.
4. The formatter resumes its second pass and reads the saved name from
released module storage, which can fault in string().
Hold key->sem for reading across kasprintf(). The collector then cannot
retype the key or complete retirement until both formatting passes have
finished. If retirement wins the lock first, formatting uses the core
key_type_dead name instead. Release the semaphore immediately after
kasprintf(), including on allocation failure, before copying to
userspace.
Oops report as below:
BUG: unable to handle page fault for address: fffffbfff8054794
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
RIP: 0010:string+0x23f/0x470
Call Trace:
vsnprintf+0x330/0x1110
Cc: [email protected]
Fixes: aa9d443 ("KEYS: Fix the size of the key description passed to/from userspace")
Assisted-by: LLM
Signed-off-by: Cen Zhang <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
Link: https://lore.kernel.org/r/pm-key-management-objects-candidate-0009-v4-6b537c5732fd957c33fa@gmail.com
Signed-off-by: Jarkko Sakkinen <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
security/keys/keyctl.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=19c4de819e52b7f606468fbfe4fcef4e812e2777
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99224 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99224
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:H/UI:N/S:U/C:L/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H
The Best / paranoid CVSS score: 5.3
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: 3
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: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0
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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