[CVE-2026-98925][LOW] bpf, sockmap: Fix self-redirect copied_seq double-counting [ Upstream

[CVE-2026-98925][LOW] bpf, sockmap: Fix self-redirect copied_seq double-counting [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98925
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: bpf, sockmap: Fix self-redirect copied_seq double-counting [ Upstream
Commit: cf9aefb26a071cb8b6fdd761c27e022a1184946d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cf9aefb26a071cb8b6fdd761c27e022a1184946d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98925
Analysis date: Tue, 27 Oct 2026 01:11:41 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A BPF sockmap self-redirect double-counts TCP receive sequence accounting, causing warnings and disruption of the configured connection without evidence of memory corruption or security-boundary bypass.

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

The original Linux kernel CVE announcement for CVE-2026-98925 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98925

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: LOW
Manual review required: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-98925	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98925 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=LOW RESULT=DIFF (final Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE)	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:N/A:L';CWE-682;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '3.7';DESCR 'A sequence accounting logic bug occurs when a BPF stream_verdict program redirects an skb to the same TCP socket with BPF_F_INGRESS. tcp_eat_skb advances copied_seq in the redirect path, and tcp_bpf_recvmsg_parser later advances it again through copied_from_self, leaving copied_seq ahead of the actual data sequence and triggering warnings in TCP receive and cleanup processing. The demonstrated impact is disruption of receive processing on the affected connection. There is no evidence of UAF, OOB access, arbitrary write, information disclosure, or privilege escalation. For the CVSS the base PR:L reflects that a local process normally needs access to a configured sockmap and affected socket. For the CVSS the worst case PR:N applies only after a privileged component has already installed a self redirect policy and an unauthenticated network peer can trigger the path by sending TCP data. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 3.7 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were KPANIC_UNSUPPORTED_REMOVED and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	REMOTE BPF SKB LINUS KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1.
* Conservative score: 1; no floor or cap applies.
* Raw paranoid score: 1.
* Paranoid score: 1; no technically supported stronger primitive.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 limited availability impact: double advancement of `tcp_sk->copied_seq` disrupts receive processing on the affected connection and triggers TCP consistency warnings.
* +0 weak bookkeeping corruption: the changed state is a sequence-accounting value, not a demonstrated memory overwrite, lifetime violation, or protected-state corruption.
* No remote-reachability bonus: network traffic reaches the path only after a BPF stream-verdict/self-redirect configuration is installed.
* No kernel-crash bonus: the evidence shows `WARNING`s and connection disruption, not panic or host-wide fatal failure.
* No UAF, OOB access/write, controlled corruption, disclosure, authorization bypass, or privilege escalation is shown.
* NEW52 B5-R does not apply: there is no heap OOB write, retry-accumulated index, or later consumption of OOB-corrupted structured storage.
* No C/I or extra availability point is awarded.

3. Reachability analysis

The immediate data-path event may be induced by TCP data once a socket, psock/sockmap, BPF program, and self-redirect policy exist. The evidence does not establish whether one below-host-admin actor can perform the complete BPF load, map setup, attachment, socket control, and trigger sequence. Namespace-scoped capability sufficiency is likewise unresolved. A remote peer may exercise an already configured path, but that prior privileged setup prevents classifying this as directly remote reachable. No race, unusual hardware, or retry sequence is involved.

4. Primitive and severity reading

The exact defect is deterministic double accounting of active TCP `copied_seq`: `tcp_eat_skb()` advances it during self-redirect, then `tcp_bpf_recvmsg_parser()` advances it again. The later TCP receive path detects the inconsistent sequence state. This is CLASS_C invalid-state/limited-DoS behavior, not a UAF or memory-corruption primitive. No privileged consumer turns the bad value into a demonstrated cross-boundary operation. ImportantCandidate is therefore NO, and auto-downgrade remains allowed.

5. One-sentence report phrase

A BPF sockmap self-redirect double-counts TCP receive sequence accounting, causing warnings and disruption of the configured connection without evidence of memory corruption or security-boundary bypass.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm product-specific BPF setup privileges and whether warnings become fatal under configured panic policies.

7. Call-site confidence

Call-site confidence: high

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

Patch: bpf, sockmap: Fix self-redirect copied_seq double-counting [ Upstream
Commit: cf9aefb26a071cb8b6fdd761c27e022a1184946d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cf9aefb26a071cb8b6fdd761c27e022a1184946d

Changed files:
  net/ipv4/tcp.c
  net/core/skmsg.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=cf9aefb26a071cb8b6fdd761c27e022a1184946d

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

The original Linux kernel CVE announcement for CVE-2026-98925 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98925

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:L/PR:L/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:N/A:L
  The Best / paranoid CVSS score: 3.7

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: 1

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).