[CVE-2026-80875][MODERATE 7.0] ipvs: use parsed transport offset in TCP state lookup [ Upstream

[CVE-2026-80875][MODERATE 7.0] ipvs: use parsed transport offset in TCP state lookup [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80875
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ipvs: use parsed transport offset in TCP state lookup [ Upstream
Commit: 2d06e0897ce18228d199887f0823b431d841dd03
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2d06e0897ce18228d199887f0823b431d841dd03
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80875
Analysis date: Fri, 04 Sep 2026 17:37:01 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate
Manual review required: YES

Summary:
No one-sentence report phrase was found.

======================================================================
ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-80875 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80875

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-2026-80875	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80875 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L';*CWE-20;CWE-682;CWE-754;Other CVSS 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '6.5';DESCR 'IPVS TCP state handling can parse the wrong bytes as a TCP header for IPv6 packets that carry extension headers because it used a fixed IPv6 header size instead of the parsed transport offset. A remote host can trigger the affected path by sending IPv6 TCP traffic with extension headers to an IPVS virtual service, causing incorrect TCP state transitions and possible connection handling failures. For the CVSS the PR:N is used because no local account or authenticated user context is needed when the IPVS service is reachable over the network. The issue is network reachable through packet traffic rather than a local control interface. Impact is mainly denial of service for affected flows or IPVS state handling. A limited integrity impact is defensible in the paranoid score because the load balancer connection state can be updated from misparsed header data.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate (with actual score 5)  SKIP CVE-2026-80875 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	REMOTE DANGER SIMPLEFIX NETFILTER NETWORK SKB LINUS IPV6 KPANIC PACKET 	-	-	checked

======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 4. No floor or cap applied.
* Raw paranoid score: 5
* Paranoid score: 5. No floor or cap applied.
* Final recommended bucket: **Actionable Moderate**::

2. Signal breakdown

Conservative signals:

* +2 Remote reachable / directly network-triggerable. An attacker can send IPv6 TCP packets with extension headers to an exposed IPVS virtual service and reach the affected TCP state handling path.
* +1 Common networking packet-processing path. The bug is in IPVS TCP state tracking under netfilter-style packet processing, not only a local configuration helper.
* +1 Availability impact realistic. Misparsed TCP header bytes can cause incorrect TCP state transitions and connection handling failures for affected flows.

Conservative non-awarded signals:

* +0 Real UAF. No stale object lifetime violation is established.
* +0 Memory corruption. `skb_header_pointer()` performs bounded header access, and the patch does not establish OOB write, UAF, double free, or arbitrary write.
* +0 Confidentiality. No read-back or disclosure path is shown.
* +0 Strong integrity impact. Wrong IPVS connection state is plausible, but no protected kernel object overwrite or security-boundary bypass is established.
* +0 Reliable kernel crash. The supplied evidence indicates wrong state lookup and connection handling failure, not kernel panic.
* +0 Race or timing. This is deterministic packet parsing logic, not a race.
* +0 Host-admin penalty. The attacker path is packet traffic to an already reachable IPVS service, not local host administration.

Paranoid additional signal:

* +1 Weak semantic/state reinterpretation concern. For IPv6 packets with extension headers, attacker-controlled bytes from the extension-header area may be interpreted as a TCP header and used to update IPVS TCP state. This supports limited state-integrity concern, but not Class A semantic reinterpretation because no ownership, pointer, descriptor, callback, or privileged resource primitive is established.

Paranoid non-awarded signals:

* Strong semantic reinterpretation +2 not awarded. The wrong bytes affect protocol state, but they do not represent kernel pointers, object ownership, credentials, descriptors, or another strong active security primitive.
* Strong LPE +2 not awarded. No controlled reclaim, arbitrary write, credential manipulation, or privilege escalation path is established.
* Extra availability +1 not awarded. There is no distinct persistent host-wide availability consequence beyond affected connection/state handling.
* ImportantCandidate not set. This is network reachable and actionable, but the primitive remains invalid protocol-state interpretation rather than kernel memory corruption or a boundary bypass.

3. Reachability analysis

A remote network peer can trigger the affected path by sending IPv6 TCP traffic with extension headers to an IPVS virtual service. The vulnerable code uses a fixed IPv6 header size when locating the TCP header, while the already parsed transport offset in `iph.len` points past extension headers to the real TCP header.

The evaluated attacker is a remote packet sender. No local account is required. No host-admin privilege is required by the attacker once an IPVS IPv6 virtual service is exposed. There is prior administrative setup in the operational sense because IPVS must be configured, but that is normal service deployment and not part of the attacker privilege requirement.

Namespace-scoped privilege is not relevant to the remote packet-trigger model. No special hardware, firmware, or race timing is required. Exposure depends on whether IPVS with IPv6 is enabled and reachable by untrusted traffic.

4. Primitive and severity interpretation

The exact primitive is a wrong transport-header offset in IPVS TCP state lookup. IPv6 packets with extension headers cause TCP state handling to inspect bytes at `sizeof(struct ipv6hdr)` instead of the parsed transport offset. Those bytes may belong to IPv6 extension headers rather than the TCP header.

This is not active structured UAF and not fixed stale storage. There is no concrete repeated release or refcount operation. There is no first lifetime operation that may free an object and no second lifetime mutation through a dangling reference.

PrimitiveClass is CLASS_C because the demonstrated behavior is invalid protocol-state parsing and incorrect state handling without an independently useful corruption primitive. The demonstrated consequence is connection handling failure or degraded IPVS behavior for affected flows. A speculative consequence is limited state-integrity impact in the IPVS connection state machine, but not kernel memory corruption or LPE.

ImportantCandidate is NO because there is no memory corruption, UAF, authorization bypass, controlled write, protected-resource access, or demonstrated privilege escalation. AutoDowngradeAllowed is NO because the issue is directly network reachable in packet processing and the limited state-integrity effect should not be automatically closed without confirming product exposure to IPv6 extension-header traffic.

Likely operational severity is Actionable Moderate.

5. One-sentence report phrase

A remote peer can send IPv6 TCP packets with extension headers to an exposed IPVS service and cause TCP state handling to parse the wrong bytes as the TCP header, leading to incorrect connection state transitions and possible denial of service for affected flows.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the issue is network reachable in an IPVS packet-processing path, and product exposure depends on whether IPv6 IPVS virtual services are reachable by untrusted traffic.

7. Call-site confidence

Call-site confidence: high

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: ipvs: use parsed transport offset in TCP state lookup [ Upstream
Commit: 2d06e0897ce18228d199887f0823b431d841dd03
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2d06e0897ce18228d199887f0823b431d841dd03

Changed files:
  net/netfilter/ipvs/ip_vs_proto_tcp.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=2d06e0897ce18228d199887f0823b431d841dd03

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-80875 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80875

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:L/PR:N/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
  The Best / paranoid CVSS score: 6.5

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: 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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).