* [CVE-2026-80885][MODERATE REGULAR] afs: Fix uncancelled rxrpc OOB message handler
@ 2026-09-04 18:03 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-04 18:03 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-80885
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: afs: Fix uncancelled rxrpc OOB message handler
Commit: 231414253b648b3518b56f09710b831945d6a2fc
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=231414253b648b3518b56f09710b831945d6a2fc
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80885
Analysis date: Fri, 04 Sep 2026 14:03:14 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80885 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80885
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 REGULAR
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-2026-80885 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80885 CHECK WITH IMPACT FROM ORIG NN NONE 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-362;*CWE-416;*CWE-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'An uncancelled AFS/RXRPC OOB work item can run after the AFS socket or net namespace is being torn down. The worker may then access net socket state that is no longer live, creating a race based use-after-free candidate and a likely kernel crash. A network peer able to send RXRPC OOB challenge traffic may help trigger the vulnerable path, but reliable exploitation also depends on local AFS activity and teardown timing. For the CVSS the PR:L is used because a local process or reduced privilege namespace context may be needed to drive the AFS or net namespace lifecycle. The issue is not a simple packet-only remote attack. Impact is at least local denial of service via kernel crash and in the paranoid case may allow confidentiality or integrity impact due to the UAF candidate, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) SKIP CVE-2026-80885 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE OOB DISK SIMPLEFIX SKIP LINUS INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP - - checked
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ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 3
* Conservative score: 4
* Raw paranoid score: 3
* Paranoid score: 4
* Applied conservative floor/cap: Real UAF floor 4 applied, 3 -> 4.
* Applied paranoid floor/cap: Real UAF floor 4 applied, 3 -> 4.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
Positive signals:
* +2 Real UAF / async lifetime violation: rx_oob_work can remain queued while afs_close_socket() tears down the AFS socket and related net state. The worker can later use net->socket after the socket lifetime is no longer protected.
* +1 Reliable kernel crash / DoS concern: stale work accessing a released socket or no longer live net namespace can plausibly produce an Oops or kernel crash.
Negative signals:
* No -2 host-admin penalty: host-admin-equivalent privilege is not positively established from the supplied patch.
* No -1 race penalty: the bug is timing/lifetime related, but the evidence does not prove a materially narrow or externally uncontrollable race beyond normal async work teardown ordering.
* No -1 rare subsystem penalty: AFS/RXRPC is specialized, but the supplied evidence does not prove an unusual configuration that the attacker cannot reach once AFS is in use.
Important non-awarded signals:
* Remote reachable +2 not awarded: RXRPC OOB challenge traffic may help reach the path, but the complete trigger also depends on local AFS socket or namespace teardown. This is not a simple packet-only remote trigger.
* Local unprivileged trigger +1 not awarded: ordinary below-host-admin reachability for the complete trigger is not established.
* NamespaceScopedPrivilege=YES not awarded: the patch involves net->live and namespace teardown, but the complete AFS setup, OOB delivery, and teardown chain is not proven to be attacker-created namespace scoped.
* Structured stale-object leverage +1 not awarded: the stale object is active structured socket/net state, but the demonstrated stale use is teardown/worker cleanup style and no meaningful attacker-controlled replacement or post-free field consumption is established.
* Weak LPE +1 not awarded: the evidence shows a UAF candidate and likely crash, not a concrete privilege-escalation primitive.
* Strong LPE / strong exploitation leverage +2 not awarded: no controlled reclaim, object replacement, callback control, arbitrary write, refcount takeover, or demonstrated LPE is shown.
* Concrete repeated release/refcount +1 not awarded: the patch does not show first release of the exact same reference followed by a second concrete lifetime/refcount mutation on that same dangling reference.
* Extra Availability +1 not awarded: the availability impact is the same likely crash/Oops already counted.
* C/I impact not awarded: confidentiality and integrity effects are speculative and not supported by a concrete readback, write, disclosure, or security-boundary bypass.
Repeated release/refcount checklist:
* First release can end lifetime: sock_release(net->socket) can end socket lifetime, but the patch does not show the same exact socket reference later receiving another lifetime-mutating release.
* Exact same reference survives to second release: not established.
* Second operation is a real lifetime/refcount mutation: not established.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 applied: no. The required concrete second lifetime/refcount mutation or other meaningful exploitation surface is not established.
3. Reachability analysis
The most plausible trigger is compound. A network peer may send RXRPC OOB challenge traffic that causes afs_rx_notify_oob() to queue rx_oob_work, while a local action or namespace teardown closes the AFS socket through afs_close_socket(). The vulnerable condition is therefore network-assisted but not independently remote in the evidence supplied.
The local privilege boundary is unresolved. AFS use and mount/setup commonly involve administrative configuration, keys, or mount privileges, but the prompt does not positively establish that host-admin-equivalent privilege is required for the complete vulnerable sequence. Therefore HostAdminRequired=UNKNOWN rather than YES.
The patch references net->live and namespace teardown, but a net namespace appearing in the lifetime path does not prove that an ordinary attacker can create the complete AFS/RXRPC setup, receive OOB challenge traffic, and drive teardown entirely inside attacker-controlled namespaces. Therefore NamespaceScopedPrivilege=UNKNOWN.
Prior setup likely includes AFS/RXRPC being enabled and in use, plus an AFS socket and remote peer capable of OOB challenge traffic. No special hardware is required. The timing is asynchronous work versus socket close/namespace teardown; it is a real lifetime ordering issue, but the supplied evidence does not justify an additional hard-race penalty.
4. Primitive and severity interpretation
The exact primitive is an uncancelled asynchronous work item using AFS/RXRPC socket state after the socket or net namespace is being torn down. This is a real lifetime violation and UAF candidate involving active structured kernel state rather than a passive bookkeeping bug.
The stale use is primarily cleanup/teardown related. The patch adds cancellation of rx_oob_work during socket close, queues OOB processing on afs_wq so it is covered by workqueue synchronization, and prevents OOB handling when the AFS net namespace is no longer live.
This is PrimitiveClass=CLASS_B because a real kernel lifetime/UAF primitive is directly implied. It is not CLASS_A because there is no controlled reclaim, directed kernel write, attacker-shaped replacement object, callback hijack, information disclosure, or demonstrated privilege escalation. It is not CLASS_C because the issue is more than a mere invalid state or warning: uncancelled work can access post-lifetime socket state.
Demonstrated consequence is likely denial of service through kernel crash or Oops. Speculative consequences include possible confidentiality or integrity impact if a separate reuse/control primitive existed, but that is not established by the patch or supplied context and is not scored.
ImportantCandidate=NO because this appears to be a constrained async teardown UAF with crash/DoS as the supported consequence and no concrete repeated refcount mutation or meaningful reuse leverage. AutoDowngradeAllowed=YES because automatic Important preservation would overstate the current evidence, though manual review remains recommended due to the real UAF in a network-related path.
Likely operational severity is borderline Moderate with manual review recommended, not a strong Important candidate on the supplied evidence alone.
5. One-sentence report phrase
An uncancelled AFS/RXRPC OOB work item may run after AFS socket or net namespace teardown and access stale socket state, causing a likely local or network-assisted kernel crash while stronger exploitation beyond DoS is not established.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Reason: this is a real async lifetime/UAF candidate in AFS/RXRPC socket teardown, but the supplied evidence supports crash/DoS only and does not establish controlled reuse, repeated refcount mutation, information disclosure, integrity impact, or LPE.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: afs: Fix uncancelled rxrpc OOB message handler
Commit: 231414253b648b3518b56f09710b831945d6a2fc
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=231414253b648b3518b56f09710b831945d6a2fc
Commit description:
Fix AFS to cancel its OOB message processing (typically to respond to
security challenges). Also move OOB message processing to afs_wq so that
it's also waited for and make the OOB handler just return if the net
namespace is no longer live.
Fixes: 5800b1c ("rxrpc: Allow CHALLENGEs to the passed to the app for a RESPONSE")
Link: https://sashiko.dev/#/patchset/20260609140911.838677-1-dhowells%40redhat.com
Signed-off-by: David Howells <[email protected]>
cc: Li Daming <[email protected]>
cc: Ren Wei <[email protected]>
cc: Marc Dionne <[email protected]>
cc: Jeffrey Altman <[email protected]>
cc: Simon Horman <[email protected]>
cc: [email protected]
cc: [email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
fs/afs/cm_security.c
fs/afs/rxrpc.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=231414253b648b3518b56f09710b831945d6a2fc
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80885 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80885
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:N/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: unknown
Paranoid ActionableScore: 4
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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR
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).
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