* [CVE-2026-98230][MODERATE 7.0] xfrm: use hlist_del_init_rcu for state_cache and state_cache_input
@ 2026-10-09 15:06 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-09 15:06 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98230
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: xfrm: use hlist_del_init_rcu for state_cache and state_cache_input
Commit: fb38fb7420d5f7192f9e2b6ac835ede149cd7ac5
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb38fb7420d5f7192f9e2b6ac835ede149cd7ac5
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98230
Analysis date: Fri, 09 Oct 2026 11:06:06 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
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-2026-98230 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98230
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-2026-98230 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98230 CHECK WITH IMPACT FROM ORIG NN MODERATE | 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:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A repeated __xfrm_state_delete operation can delete the same state_cache or state_cache_input node twice because hlist_del_rcu leaves pprev set to LIST_POISON2 and hlist_unhashed therefore does not recognize the node as unhashed. The second deletion can write through a poisoned or stale pprev pointer after the xfrm_state allocation has been freed or reused, creating a write use after free. The resulting list corruption can later make an RCU traversal in xfrm_input_state_lookup follow a dangling next pointer and trigger a read use after free. Impact is at least a local denial of service through memory corruption and a kernel crash. In the worst defensible case, corruption of a reused slab object may affect confidentiality and integrity or support local privilege escalation. For the CVSS the PR:L value is used for the paranoid score because a reduced capability process, container root, or service with delegated CAP_NET_ADMIN may be able to reach XFRM state management without having unrestricted host root privileges. AC:H reflects the need to cause a repeated deletion with suitable object lifetime and slab reuse timing. The issue is not shown to be directly triggerable by arbitrary network packets alone, although network traffic may reach the corrupted XFRM lookup path after the initial state corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE DANGER INIT UAF LINUS KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
1. ActionableScore
* Raw conservative score: 4
* Conservative score: 5
* Raw paranoid score: 4
* Paranoid score: 5
* Applied conservative floor: 4 -> 5 under REAL UAF FLOOR 5 because an active structured XFRM cache is corrupted and the stale list state is later consumed by an RCU packet-processing lookup.
* Applied paranoid floor: 4 -> 5 for the same established mechanism. No additional speculative exploitation point was added.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
Positive signals:
* +2 Real UAF and lifetime violation. A second deletion operates on an already deleted cache node after its original lifetime may have ended or its slab may have been reused.
* +1 Secondary index and hash-list staleness. Incorrect removal semantics leave `state_cache` or `state_cache_input` in a state that permits another unlink and can corrupt links later traversed by `xfrm_input_state_lookup`.
* +1 Reliable kernel crash or strong DoS. Writing through `LIST_POISON2` or following the resulting dangling list pointer can produce a kernel fault.
Raw total: 2 + 1 + 1 = 4.
Not awarded:
* No remote-reachability bonus. Network packets can reach the later XFRM lookup, but the evidence does not show that arbitrary traffic can independently cause the required second state deletion.
* No local-unprivileged bonus. The complete path to repeated `__xfrm_state_delete()` is not supplied.
* No strong exploitation-leverage bonus. Controlled reclaim, attacker-selected destination, attacker-controlled replacement contents, arbitrary write, callback control, and refcount takeover are not demonstrated.
* No weak-LPE point. Slab reuse is stated, but meaningful attacker control over the reused object is not established.
* No separate structured stale-object leverage point. Later RCU traversal is established, but attacker influence over the replacement or dangling link contents is unresolved.
* No extra Availability point. The same crash is counted only once.
* No Confidentiality or Integrity point. The write UAF is concrete, but disclosure, protected-state modification, and privilege escalation are not demonstrated.
* No race penalty. The input does not establish a narrow or externally uncontrollable timing window.
* No privilege penalty. Host-admin-equivalent privilege is not positively established.
* B5-R does not apply. There is no retry-accumulated index or heap OOB write. This is a repeated hash-list deletion and UAF profile instead.
Repeated-release and refcount checks:
* The first operation removes the node but is not itself a reference-count decrement or object lifetime release.
* The same embedded node can reach a second list deletion.
* The second operation mutates list linkage through a stale `pprev`, not an object lifetime refcount.
* Concrete repeated release or refcount +1 was not awarded.
* Paranoid repeated-refcount leverage +1 was not awarded.
* FLOOR 5 was applied because the established corruption escapes deletion processing and is later consumed during active structured XFRM lookup, not because of the repeated-refcount rule.
3. Reachability analysis
The initiating actor is unresolved. XFRM state management commonly uses privileged netlink control operations, but the supplied patch does not expose the call paths that cause the second `__xfrm_state_delete()` or identify the governing capability check.
Incoming traffic may subsequently exercise `xfrm_input_state_lookup()` and consume the corrupted cache links. That does not prove a network-only trigger because the attacker must first cause the repeated deletion and corrupted cache state.
It is unknown whether the complete sequence can be performed with namespace-scoped `CAP_NET_ADMIN`, by a delegated network-management service, or only through host-admin-controlled XFRM state management. Therefore both host-admin and namespace-scoped privilege remain UNKNOWN. No prior setup, special hardware, or unusually rare configuration is established. Race repeatability also remains unresolved.
4. Primitive and severity interpretation
The exact primitive is a write use-after-free or stale-node write during a second `hlist_del_rcu()` operation, followed by possible read use-after-free when an RCU cache traversal follows a dangling `next` pointer.
The affected state is an active structured object and secondary lookup structure, not fixed stale storage. The first observable write may fault immediately through `LIST_POISON2`, but the commit also establishes a post-reuse corruption case and later active consumption in `xfrm_input_state_lookup()`.
This is not a concrete repeated release or refcount mutation. It is repeated list unlinking through stale linkage, so it remains CLASS_B rather than becoming CLASS_A. Demonstrated consequences are list corruption, read UAF, and kernel crash. Arbitrary read or write, controlled reclaim, information disclosure, and privilege escalation remain speculative.
ImportantCandidate is YES because a concrete write UAF corrupts an active RCU lookup structure and the resulting state is consumed outside the deletion path. AutoDowngradeAllowed is NO because automatically treating it as an ordinary crash-only list bug could discard unresolved exploitation leverage from slab reuse and active packet-path traversal. The practical evidence supports Actionable Moderate at minimum, with Important classification requiring call-path and reclaim analysis.
5. One-sentence report phrase
A repeated XFRM state deletion can write through stale hash-list linkage after slab reuse and leave a dangling pointer for later RCU packet-path traversal, creating write and read use-after-free conditions that require mandatory exploitation and reachability review.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Review the callers of `__xfrm_state_delete()`, the path permitting a second deletion, slab reuse controllability, namespace capability checks, and whether corrupted cache links can provide useful behavior beyond an immediate poison-pointer crash.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: xfrm: use hlist_del_init_rcu for state_cache and state_cache_input
Commit: fb38fb7420d5f7192f9e2b6ac835ede149cd7ac5
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb38fb7420d5f7192f9e2b6ac835ede149cd7ac5
Commit description:
Commit 14acf96 ("xfrm: defensively unhash xfrm_state lists in
__xfrm_state_delete") converted bydst/bysrc/byseq/byspi from
hlist_del_rcu() to hlist_del_init_rcu() so that a second
__xfrm_state_delete() on the same object becomes a no-op rather than a
write through LIST_POISON pprev. It missed state_cache and
state_cache_input, which kept hlist_del_rcu():
- hlist_del_rcu() leaves pprev = LIST_POISON2 (non-NULL), so
hlist_unhashed() returns false.
- hlist_del_init_rcu() leaves pprev = NULL, so hlist_unhashed()
returns true.
A second __xfrm_state_delete() therefore enters __hlist_del() on the
already-deleted state_cache/state_cache_input nodes and does
WRITE_ONCE(*pprev, next) through LIST_POISON2 — a write use-after-free
once the slab is reused. The corruption can in turn cause a subsequent
hlist_for_each_entry_rcu traversal to follow a dangling next pointer,
producing the read use-after-free reported in xfrm_input_state_lookup().
Switch state_cache and state_cache_input to hlist_del_init_rcu() to
match the other four lists, closing the write use-after-free and, with
it, the read use-after-free it spawns.
Assisted-by: CodeBuddy:GLM-5.2
Fixes: 0045e3d ("xfrm: Cache used outbound xfrm states at the policy.")
Fixes: 81a331a ("xfrm: Add an inbound percpu state cache.")
Cc: [email protected]
Signed-off-by: Siwei Zhang <[email protected]>
Signed-off-by: Steffen Klassert <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
net/xfrm/xfrm_state.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=fb38fb7420d5f7192f9e2b6ac835ede149cd7ac5
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98230 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98230
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: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: unknown
Paranoid ActionableScore: 5
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).
^ 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 --
2026-10-09 15:06 21% [CVE-2026-98230][MODERATE 7.0] xfrm: use hlist_del_init_rcu for state_cache and state_cache_input AL-KERNEL
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox