[CVE-2026-68477][MODERATE REGULAR] ipvs: fix more places with wrong ipv6 transport offsets

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-68477
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ipvs: fix more places with wrong ipv6 transport offsets
Commit: 613ce63711b8d431bba90781f133c39a21684f87
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=613ce63711b8d431bba90781f133c39a21684f87
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68477
Analysis date: Sat, 15 Aug 2026 04:55:01 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
IPVS used incorrect IPv6 transport offsets in TCP app and ICMPv6 handling, allowing remote IPv6 traffic with extension headers to cause incorrect packet processing in configured IPVS deployments.

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

The original Linux kernel CVE announcement for CVE-2026-68477 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68477

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-2026-68477	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L';CWE-682;*CWE-20;CWE-754;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.8';DESCR 'IPVS used IPv4 header length logic when locating the TCP header for IPv6 app processing, and used a fixed IPv6 header length for an ICMPv6 checksum path. IPv6 packets with extension headers can therefore be parsed at the wrong transport offset, causing incorrect application helper behavior or checksum handling in configured IPVS services. For the CVSS the PR:N is selected because a remote peer only needs network reachability to the affected virtual service and does not need local access on the target. The issue is network reachable only when IPVS is configured for IPv6 traffic and a relevant app or ICMPv6 path is used. Impact is mainly limited service disruption or packet handling integrity loss, with no evidence of kernel memory corruption or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 4)	YES	REMOTE SIMPLEFIX NETFILTER SKB LINUS IPV6 PACKET  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2
  A remote peer can potentially trigger the affected paths by sending IPv6 traffic with extension headers to a configured IPVS virtual service.
* Common networking / packet-processing path: +1
  The bug is in IPVS packet handling under netfilter, not a purely local ioctl or admin-only control path.

Paranoid additional signal:

* Integrity impact plausible: +1
  Wrong transport offsets may cause incorrect app-helper behavior or ICMPv6 checksum handling. This supports limited packet-processing integrity impact, but not kernel memory corruption.

Not awarded:

* No generic memory corruption signal. The patch fixes offset calculation, but does not show UAF, OOB write, double free, type confusion, or arbitrary write.
* No privilege escalation signal. There is no supported LPE primitive.
* No strong DoS signal. The commit says the in-tree FTP app case is harmless and does not describe crash, panic, or reliable system-wide failure.

## 3. Reachability analysis

The likely trigger is a remote network peer sending IPv6 packets with extension headers through an IPVS-configured service. The attacker does not need local code execution or privileges on the target, so attacker-side reachability is PR:N in CVSS terms. The target must have IPVS enabled and configured for IPv6, and the affected app or ICMPv6 path must be exercised. This is not Internet-default exposure on ordinary hosts, but it is realistic in load-balancer deployments. Namespaces mainly affect who can configure IPVS, not who can send triggering packets once the service is exposed.

Call-site confidence: medium. The changed paths are packet-processing call sites in the provided diff, but full downstream behavior of all possible IPVS apps is not shown.

## 4. Severity interpretation

This behaves like a borderline or actionable Moderate networking correctness issue, not an Important-class kernel vulnerability. The realistic impact is malformed or incorrect packet handling for IPv6 extension-header cases in configured IPVS deployments. Theoretical impact includes limited service disruption or packet-processing integrity problems, but the patch does not support memory corruption, information disclosure, or privilege escalation.

## 5. One-sentence report phrase

IPVS used incorrect IPv6 transport offsets in TCP app and ICMPv6 handling, allowing remote IPv6 traffic with extension headers to cause incorrect packet processing in configured IPVS deployments.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: network-reachable packet parsing bugs in netfilter/IPVS deserve review, but current evidence supports only limited packet-handling impact and does not show memory corruption or privilege escalation.

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

Patch: ipvs: fix more places with wrong ipv6 transport offsets
Commit: 613ce63711b8d431bba90781f133c39a21684f87
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=613ce63711b8d431bba90781f133c39a21684f87

Commit description:

Sashiko reports for more incorrect IPv6 transport offsets.

The app code for TCP was assuming IPv4 network header
even after the ipvsh argument was provided. This can
cause problems with apps over IPv6. As for the only
official app in the kernel tree (FTP) this problem is
harmless because we use Netfilter to mangle the FTP
ports and we do not adjust the TCP seq numbers.

Also, provide correct offset of the ICMPV6 header in
ip_vs_out_icmp_v6() for correct checksum checks when
the IPv6 packet has extension headers.

Fixes: d12e122 ("ipvs: add ipv6 support to ftp")
Fixes: 2a3b791 ("IPVS: Add/adjust Netfilter hook functions and helpers for v6")
Cc: stable@vger.kernel.org
Link: https://sashiko.dev/#/patchset/20260706101624.69471-1-zhaoyz24%40mails.tsinghua.edu.cn
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/netfilter/ipvs/ip_vs_app.c
  net/netfilter/ipvs/ip_vs_core.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=613ce63711b8d431bba90781f133c39a21684f87

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

The original Linux kernel CVE announcement for CVE-2026-68477 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68477

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:L
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L
  The Best / paranoid CVSS score: 4.8

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: 3
  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).

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).