* [CVE-2026-89777][IMPORTANT] vfio/pci: clear vdev->msi_perm after freeing it on init failure [ Upstream
@ 2026-09-16 9:07 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-16 9:07 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89777
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: vfio/pci: clear vdev->msi_perm after freeing it on init failure [ Upstream
Commit: eb84cd81040e58dd05ac190f561f2115e3367249
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=eb84cd81040e58dd05ac190f561f2115e3367249
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89777
Analysis date: Wed, 16 Sep 2026 05:07:08 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89777 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89777
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: IMPORTANT
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-2026-89777 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-89777 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-415;*CWE-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A dangling pointer in vfio/pci can remain in vdev msi_perm after an init failure because the object is freed but the stored pointer is not cleared. A later open or config access can reuse the stale pointer and vfio_pci_config_rw_single can dereference freed permission data including readfn and writefn callback pointers. The same stale object can also be freed again during device close, creating a double free path. For the CVSS the PR:L is used because triggering requires local access to a VFIO PCI device or a process context that can open and operate that assigned device, but it does not necessarily require full host root in deployments where VFIO access is delegated to a VM or service user. The issue is not network reachable and is triggered through the local VFIO device interface. Impact is at least a local denial of service via kernel crash and in the paranoid case may include privilege escalation because the bug is a kernel use after free involving callback pointers.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6) YES READ OOB LEAK ERRORPATH UAF HARDWARE LINUS KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
1. ActionableScore
* Raw conservative score: 5
* Conservative score: 5
* Raw paranoid score: 6
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
No floor or cap changed the conservative score. No floor or cap changed the paranoid score.
2. Signal breakdown
Conservative positive signals:
* +2 Real UAF / lifetime violation. `vdev->msi_perm` is freed on the init failure path but the pointer remains stored in the persistent `vfio_pci_core_device`, so later open/config paths can use a stale post-lifetime object.
* +1 Reliable kernel crash / strong DoS. The supplied trace shows KASAN slab-use-after-free in `vfio_pci_config_rw_single()` and later a fatal double-free path ending in kernel panic.
* +1 Concrete repeated release/free operation. The first `kfree(vdev->msi_perm)` can end the object lifetime, the exact same pointer survives in `vdev->msi_perm`, and later `vfio_config_free()` can run cleanup and `kfree()` on the same already-freed object.
* +1 Structured stale-object exploitation leverage. The stale object is not only passed to cleanup. The later config access consumes freed permission data and may call stale `perm->readfn` / `perm->writefn` callback pointers. Controlled reclaim is not demonstrated, so this is not scored as CLASS_A.
Paranoid additional signal:
* +1 Paranoid repeated-refcount/free leverage. The second lifetime operation is a concrete write-like allocator/lifetime mutation through storage whose original object lifetime may already have ended. This leaves unresolved post-free corruption leverage beyond an ordinary stale read, but still does not prove controlled reclaim or arbitrary write.
Negative signals:
* No host-admin-equivalent penalty is applied. The evidence supports a local VFIO device access model and previous triage indicates PR:L rather than PR:H.
* No race/timing penalty is applied. This is an ordered init-failure and later reuse/free sequence, not a narrow timing race.
* No rare-hardware penalty is applied. VFIO PCI passthrough is specialized but not enough by itself to treat the issue as rare or physical-only.
* No remote reachability bonus is applied. The path is local through VFIO device operations.
Important non-awarded signals:
* Controlled reclaim is not demonstrated.
* Arbitrary kernel read/write is not demonstrated.
* Demonstrated LPE is not established.
* CLASS_A is not used because callback-pointer consumption is stale and dangerous, but attacker-controlled replacement contents or callback hijack are not proven.
* Weak LPE is not separately awarded because the relevant concern is already captured by structured stale-object leverage and the repeated-free signal.
* Extra availability is not awarded because the same crash/panic is already counted once.
* C/I impact is not awarded merely because the UAF and double free could theoretically corrupt reclaimed memory.
Repeated-release checklist:
* First release can end lifetime: yes, `kfree(vdev->msi_perm)`.
* Exact same reference survives: yes, `vdev->msi_perm` is not cleared until this patch.
* Second operation mutates lifetime/free state: yes, later `vfio_config_free()` can free the same object again.
* Dedicated +1 Concrete repeated release/free awarded: yes.
* Paranoid repeated-refcount/free +1 awarded: yes, because the second free is a concrete post-lifetime allocator/lifetime mutation.
* FLOOR 5 applied: not needed because conservative raw score is already 5.
3. Reachability analysis
The evaluated attacker is a local user or process with access to the relevant VFIO PCI device. This is below full host administrator in deployments where VFIO device access is delegated to a VM launcher, service account, or assigned-device user. It is not an ordinary network attack and is not triggered by remote packets.
The complete trigger requires a failed `vfio_config_init()` path where `init_pci_cap_msi_perm()` fails after `vdev->msi_perm` has been allocated, followed by a later open/config access or close path on the same persistent VFIO PCI device. The failure condition may require memory pressure, fault injection, or another allocation-failure condition, so practical reliability needs manual validation.
Namespace-scoped privilege is not established. VFIO PCI device access is not treated as a normal attacker-created user/network namespace capability. Prior host setup may exist because PCI devices are commonly assigned or permissioned by an administrator, but after delegation the vulnerable operations can be performed by the delegated local actor.
No special rare hardware assumption is used beyond the need for a VFIO PCI device. No narrow race is required.
4. Primitive and severity interpretation
The exact primitive is a real kernel use-after-free of `vdev->msi_perm`, followed by two relevant stale uses. First, a later config path can reuse the stale pointer and consume freed structured permission data, including callback function pointers. Second, a later cleanup path can double-free the same object.
This is an active structured-object UAF, not fixed stale storage. It is not cleanup-only because `vfio_pci_config_rw_single()` can consume the stale permission object during PCI config access before the later close-time double free. The repeated free path is category B from the prompt: a second lifetime/free mutation through a potentially dangling object.
PrimitiveClass is CLASS_B. It is stronger than a crash-only NULL dereference because the stale object persists across open/close cycles, is reused by normal VFIO config access, and reaches both callback-pointer consumption and double free. It is not CLASS_A because controlled reclaim, attacker-shaped replacement contents, arbitrary write, or demonstrated callback hijack are not established.
Demonstrated consequence is local kernel crash/DoS. Speculative but technically meaningful consequence is possible privilege escalation if a practical reclaim or callback-control path exists. That unresolved exploitation leverage makes this an Important-vs-Moderate manual-review case.
ImportantCandidate=YES because the bug is a real active-object UAF with stale callback-pointer consumption and a concrete double-free path. AutoDowngradeAllowed=NO because automatically closing it as ordinary Moderate would discard unresolved post-lifetime corruption leverage.
Likely operational severity is Actionable Moderate at minimum, with Strong Important candidacy requiring manual review.
5. One-sentence report phrase
A dangling `vdev->msi_perm` pointer in vfio/pci can survive an init failure and later be reused for MSI config access or freed again, creating a local kernel UAF and double-free condition with at least DoS impact and unresolved privilege-escalation relevance.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Reason: this is a concrete kernel UAF with stale structured callback-pointer consumption and a later double-free of the same object, so Important-vs-Moderate exploitation leverage remains unresolved.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: vfio/pci: clear vdev->msi_perm after freeing it on init failure [ Upstream
Commit: eb84cd81040e58dd05ac190f561f2115e3367249
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=eb84cd81040e58dd05ac190f561f2115e3367249
Changed files:
drivers/vfio/pci/vfio_pci_config.c
mm/kasan/report.c
drivers/vfio/pci/vfio_pci_core.c
fs/read_write.c
arch/x86/entry/syscall_64.c
mm/slub.c
drivers/vfio/vfio_main.c
fs/file_table.c
fs/open.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=eb84cd81040e58dd05ac190f561f2115e3367249
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89777 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89777
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:L/I:L/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7
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: 5
Paranoid ActionableScore: 6
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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT
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 --
2026-09-16 9:07 21% [CVE-2026-89777][IMPORTANT] vfio/pci: clear vdev->msi_perm after freeing it on init failure [ Upstream AL-KERNEL
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox