* [CVE-2026-98369][MODERATE 7.0] xfrm: add missing rcu_read_lock(), skb_dst_force() and dev_hold() for xfrm_trans_reinject() [ Upstream
@ 2026-10-08 13:03 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-08 13:03 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98369
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: xfrm: add missing rcu_read_lock(), skb_dst_force() and dev_hold() for xfrm_trans_reinject() [ Upstream
Commit: 41e47f1664be86c91326f0afe0504a1162d00907
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=41e47f1664be86c91326f0afe0504a1162d00907
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98369
Analysis date: Thu, 08 Oct 2026 09:03:38 -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-2026-98369 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98369
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-2026-98369 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98369 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE_KPANIC RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '8.1';DESCR 'A race in deferred XFRM transport mode packet reinjection can process an skb after its dst entry or network device reference is no longer valid. The workqueue callback may access RCU protected routing data and skb dev state while a concurrent network device unregister releases or replaces the underlying objects. This creates a plausible use-after-free condition that can at least cause a kernel crash. For the CVSS the PR:N because an attacker may only need to send traffic that reaches an already configured XFRM transport mode policy and does not need local access to the target. The attack complexity is high because reliable triggering requires a timing race with deferred work processing and network device teardown. The issue is network reachable only for hosts using XFRM transport mode and accepting relevant traffic. Impact is at least a network reachable denial of service and in the worst case may affect confidentiality and integrity due to potential use-after-free memory corruption. ';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE LOCK WARNONLY SKB LINUS IPV6 SYZBOT PACKET KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 4
* Raw paranoid score: 1
* Paranoid score: 4
* Applied conservative floor: 1 -> 4. A concrete stale dst or netdevice reference can be consumed by deferred workqueue packet processing, and host-admin-equivalent privilege is not positively established.
* Applied paranoid floor: 1 -> 4.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +2 Real UAF or active lifetime violation. Packets can be queued to a workqueue with a non-refcounted dst entry or without a retained reference to skb->dev. Concurrent netdevice unregistration may release or replace the referenced state before the deferred finish callback consumes it.
* -1 Hard or unreliable race. Triggering requires overlap between queued XFRM transport reinjection work and netdevice teardown or related RCU retirement. The supplied evidence does not show that one attacker can reliably drive both stages.
* +0 Direct remote reachability not awarded. XFRM transport reinjection requires an already configured XFRM path, and the supplied patch does not establish that an unauthenticated remote actor can both reach the affected deferred path and induce the required netdevice-unregister lifetime transition.
* +0 Reliable kernel crash not awarded. The supplied evidence shows an RCU lockdep warning and a concrete stale-reference condition, but does not include a demonstrated Oops, panic, or reproducible crash.
* +0 Controlled reclaim or object replacement not demonstrated. The patch establishes missing lifetime protection, not attacker-controlled reuse of freed dst or netdevice memory.
* +0 Arbitrary write, directed write, callback control, and refcount takeover not demonstrated.
* +0 Structured stale-object leverage not awarded. dst and net_device are active structured objects, but the supplied evidence does not show attacker-controlled replacement contents or useful consumption of reclaimed fields beyond the stale deferred packet-processing path.
* +0 Concrete repeated release or refcount mutation not established. dev_put is newly added after the callback to balance the new dev_hold. The patch does not show a second put, free, or refcount decrement through an already dangling exact reference.
* +0 Confidentiality and integrity impact not awarded. A potential UAF alone does not establish disclosure, unauthorized modification, or privilege escalation.
* +0 Additional availability impact not awarded. No distinct persistent availability effect beyond a possible stale-pointer fault is established.
3. Reachability analysis
The affected path is XFRM transport-mode packet reinjection deferred through a workqueue. The packet must first reach an already configured XFRM transport processing path. The supplied material does not establish whether a remote unauthenticated attacker can inject traffic accepted by the relevant IPsec/XFRM policy, because deployment may require valid security associations and authenticated traffic.
The stale-use condition additionally depends on a concurrent netdevice unregister or equivalent object-retirement event while the skb remains queued for workqueue reinjection. The patch does not establish that a remote peer can cause this teardown operation. It also does not establish that an ordinary local user can control both XFRM policy setup and network-device lifetime.
Host-admin-equivalent privilege is therefore UNKNOWN rather than YES or NO. XFRM policy and netdevice management often involve CAP_NET_ADMIN, but the exact capability checks, target namespace, and complete trigger sequence are not visible. NamespaceScopedPrivilege is UNKNOWN because the existence of network namespaces alone would not prove that all required XFRM setup, packet processing, and device teardown stages are attacker-reachable in an unprivileged namespace.
No special hardware, firmware, boot option, or unusual kernel configuration is established beyond availability of the affected XFRM transport-mode path. The key practical limitation is the asynchronous race with device lifetime handling, not hardware.
4. Primitive and severity interpretation
The patch establishes a real lifetime-protection defect. A queued skb can retain a non-refcounted dst or an skb->dev pointer without holding the reference required to preserve the destination or netdevice across workqueue deferral. The later finish callback may then operate after the object was retired, replaced, or freed. Missing rcu_read_lock also permits callbacks that expect RCU protection to access RCU-protected networking state in process context without the required read-side critical section.
This is an active structured-object lifetime issue rather than fixed stale DMA storage. However, the visible stale use is limited to deferred XFRM packet reinjection and networking finish callbacks. The patch does not establish attacker-controlled object reuse, post-free replacement contents, a callback dispatch from reclaimed memory, arbitrary read or write, information disclosure, or a security-boundary bypass.
No concrete repeated release or refcount mutation exists in the vulnerable code shown. The newly added dev_hold and dev_put form a normal matched ownership pair. This is not the stronger pattern of first put possibly freeing an object followed by a second put through the same dangling reference.
The appropriate classification is CLASS_B because a real stale post-lifetime object use is directly implied. The demonstrated practical consequence remains an RCU correctness violation and potential kernel fault or denial of service. Privilege escalation and confidentiality or integrity effects remain speculative and are not supported by a concrete exploitation primitive.
ImportantCandidate is NO because meaningful reuse or corruption leverage beyond a possible crash has not been demonstrated. AutoDowngradeAllowed is YES because this is presently a constrained lifetime bug with unresolved reachability and no demonstrated controlled reclaim, repeated lifetime mutation, security-boundary bypass, or attacker-directed corruption. Manual review remains recommended to confirm whether XFRM packet processing and netdevice teardown can be jointly driven by a below-host-admin attacker in the target product.
5. One-sentence report phrase
A deferred XFRM transport reinjection path can process an skb after its dst entry or network device reference is no longer valid, creating a potential stale-object use during concurrent device teardown and requiring review for kernel denial of service impact.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
The patch directly fixes RCU and object-lifetime protection across asynchronous workqueue processing, but the supplied evidence does not establish a reliable attacker-controlled trigger, controlled object reuse, or a non-DoS exploitation primitive.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: xfrm: add missing rcu_read_lock(), skb_dst_force() and dev_hold() for xfrm_trans_reinject() [ Upstream
Commit: 41e47f1664be86c91326f0afe0504a1162d00907
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=41e47f1664be86c91326f0afe0504a1162d00907
Changed files:
include/net/addrconf.h
net/ipv6/route.c
net/xfrm/xfrm_input.c
kernel/workqueue.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=41e47f1664be86c91326f0afe0504a1162d00907
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98369 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98369
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:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 8.1
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: 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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