* [CVE-2026-98078][MODERATE 7.0] ipvs: fix reversed sequence option serialization [ Upstream
@ 2026-09-25 16:57 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-25 16:57 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98078
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ipvs: fix reversed sequence option serialization [ Upstream
Commit: e1c9f9446d3eaae323f1689f9e5de3b1ad6e47ec
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e1c9f9446d3eaae323f1689f9e5de3b1ad6e47ec
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98078
Analysis date: Fri, 25 Sep 2026 12:57:47 -0400
ActionableScore: 6
ActionableScore lower bound: 4
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-2026-98078 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98078
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-2026-98078 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98078 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:H';*CWE-457;*CWE-200;CWE-685;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L';BEST CVSS score: '7.1';DESCR 'The IPVS version 1 synchronization sender passes the source and destination arguments to hton_seq in reverse order for both sequence blocks. As a result, 24 bytes of the kmalloc-backed synchronization message remain unwritten and may contain stale kernel heap data that is transmitted to synchronization peers. The same operation replaces the live inbound and outbound connection sequence state with values read from the uninitialized message buffer, which can corrupt sequence adjustment and disrupt affected connections. For the CVSS the PR:N value is used because no authenticated account or local user context is required if an attacker can generate relevant traffic and observe the IPVS synchronization network. The attack is adjacent network rather than general Internet reachable because IPVS synchronization traffic is normally carried over a dedicated or trusted internal network. Successful triggering also depends on IPVS version 1 synchronization being active and on a connection using sequence adjustment state. Impact includes kernel heap information disclosure and connection state corruption. Repeated triggering may expose additional stale heap data and may cause broader availability impact, but the code does not provide an arbitrary write primitive or a demonstrated privilege escalation path.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE REMOTE READ SIMPLEFIX NETFILTER KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=6
ActionableScoreLower=4
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
1. ActionableScore
* Raw conservative score: 4
* Conservative score: 4. No floor or cap applied.
* Raw paranoid score: 6
* Paranoid score: 6. No floor or cap applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
Conservative signals:
* +2 Remote or adjacent-network exposure. The vulnerable sender places uninitialized kernel heap bytes into an IPVS synchronization message. An attacker with access to the synchronization network can observe the resulting disclosure without local execution on the affected host.
* +1 Constrained kernel-state overwrite. Reversed arguments cause stale buffer values to overwrite the fixed `cp->in_seq` and `cp->out_seq` fields. The target and size are bounded, and attacker-selected contents are not established.
* +1 Confidentiality plausible. Twenty-four bytes of unwritten kmalloc-backed memory are concretely included in network-visible output.
* +1 Integrity plausible. Live connection sequence state is replaced with unintended values, potentially corrupting sequence adjustment for active connections.
* -1 Rare and difficult-to-reach configuration. The path requires IPVS version 1 synchronization, an active sync sender, sequence-option serialization, and access to the synchronization network. These requirements are directly supported by the affected path rather than inferred merely because IPVS is specialized.
Paranoid additional signal:
* +2 Strong exploitation leverage. Repeated connection synchronization can plausibly turn the fixed 24-byte disclosure into a repeatable kernel heap disclosure primitive useful for exposing pointers or other stale kernel data. This remains technically grounded in repeated calls to the same sender and does not assume arbitrary read, arbitrary write, or privilege escalation.
Not awarded:
* No UAF, OOB write, controlled reclaim, arbitrary write, callback influence, or credential corruption is established.
* No reliable kernel crash or host-wide availability point is awarded. The demonstrated integrity consequence is connection-state corruption and disruption, not a kernel panic.
* No extra practical-exploit-chain point is awarded because it would substantially duplicate the already scored network disclosure primitive.
* No local privilege-escalation point is awarded.
* No common-networking-core bonus is awarded because the vulnerable path is specific to configured IPVS synchronization.
* No namespace-scoped privilege conclusion is made because the complete setup and observation path is not shown to be attacker-created inside a user or network namespace.
3. Reachability analysis
The affected host must already be configured as an IPVS version 1 synchronization sender. That configuration normally represents prior administrative setup, but the observing attacker does not need host-administrator privileges after the synchronization service is exposed. Relevant traffic must produce a connection carrying `IP_VS_CONN_F_SEQ_MASK`, after which `ip_vs_sync_conn()` serializes both sequence blocks.
The practical attacker is an adjacent-network observer or synchronization peer that can receive or capture IPVS synchronization messages and may also generate traffic resulting in relevant connection state. This is not general public-Internet exposure unless the synchronization transport is unusually exposed.
HostAdminRequired is therefore NO for the disclosure attack itself. Prior privileged service configuration exists, but the attacker is not required to perform that configuration. NamespaceScopedPrivilege remains UNKNOWN because the supplied context does not establish that the complete IPVS setup, traffic generation, and message-observation chain can be constructed within attacker-created namespaces.
No race or narrow timing window is involved. Triggering depends on deterministic serialization conditions rather than an unreliable interleaving. No special hardware or boot mode is required.
4. Primitive and severity interpretation
The primary primitive is a concrete kernel heap information disclosure. Reversing the arguments to `hton_seq()` causes two 12-byte regions of the outbound synchronization message to remain unwritten while still being transmitted. This establishes disclosure rather than a kernel-internal invalid read with no output path.
A second primitive is a bounded and uncontrolled overwrite of active connection sequence fields. The stale message-buffer values are written into `cp->in_seq` and `cp->out_seq`. This can damage connection processing, but there is no evidence that the attacker controls the written values, selects another target, or converts the operation into arbitrary kernel memory corruption.
This is not a UAF or lifetime bug. There is no repeated release, refcount mutation, stale-object reuse, or cleanup-only dereference. The issue is CLASS_A because it provides a concrete, potentially repeatable kernel heap disclosure across a network boundary. The constrained sequence-state overwrite reinforces integrity impact but is not independently a strong corruption primitive.
The demonstrated consequences are stale kernel heap disclosure and corruption or disruption of synchronized connection state. Pointer disclosure and mitigation weakening are plausible under repeated use. Arbitrary read, arbitrary write, host compromise, and privilege escalation remain speculative and are not scored.
ImportantCandidate is YES because a repeatable network-visible kernel heap disclosure requires Important-versus-Moderate review. AutoDowngradeAllowed is NO because automatically treating this as ordinary connection corruption would discard the concrete kernel-information-disclosure primitive. The likely operational severity is Actionable Moderate, with possible Important classification depending on disclosure repeatability, allocator contents, and actual synchronization-network exposure.
5. One-sentence report phrase
Reversed `hton_seq()` arguments in the IPVS version 1 synchronization sender expose 24 bytes of stale kernel heap data per affected message and corrupt live connection sequence state, requiring manual review for repeatable information disclosure and connection disruption.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Confirm whether the disclosure is repeatable, what kmalloc cache supplies the message buffer, whether useful kernel pointers or sensitive data can appear in the leaked bytes, and which untrusted systems can observe the IPVS synchronization network.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: ipvs: fix reversed sequence option serialization [ Upstream
Commit: e1c9f9446d3eaae323f1689f9e5de3b1ad6e47ec
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e1c9f9446d3eaae323f1689f9e5de3b1ad6e47ec
Changed files:
net/netfilter/ipvs/ip_vs_sync.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=e1c9f9446d3eaae323f1689f9e5de3b1ad6e47ec
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98078 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98078
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:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:H
The Best / paranoid CVSS score: 7.1
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: 4
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: 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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