[CVE-2026-68289][MODERATE 7.0] tipc: fix integer overflow in tipc_recvmsg() and tipc_recvstream() [ Upstream

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

CVE: CVE-2026-68289
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: tipc: fix integer overflow in tipc_recvmsg() and tipc_recvstream() [ Upstream
Commit: fe9bf32bb18f2d35789d4960fb007d1059bbaa38
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fe9bf32bb18f2d35789d4960fb007d1059bbaa38
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68289
Analysis date: Mon, 10 Aug 2026 12:32:30 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: NO

Summary:
A local integer conversion flaw in the TIPC receive path can turn an oversized `buflen` into a negative copy length, reaching `simple_copy_to_iter()` as a huge size and triggering a WARN or `panic_on_warn` kernel crash.

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

The original Linux kernel CVE announcement for CVE-2026-68289 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68289

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: NO

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

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

CVE-2026-68289	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-190;CWE-681;CWE-754;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'An integer conversion flaw in the TIPC receive path can occur because tipc_recvmsg() and tipc_recvstream() used min_t(int, ...) while comparing a size_t buflen value. A local process can provide a buflen larger than INT_MAX, for example through io_uring provided buffers, causing the value to wrap to a negative int and propagate as an invalid copy length into the datagram copy path. This can trigger a WARN_ON in simple_copy_to_iter and can become a kernel panic when panic_on_warn is enabled. For the CVSS the PR:L is used because reliable triggering requires local code execution by a user or process that can call the TIPC receive path with a crafted buffer length. The issue is not directly network reachable because the dangerous length is supplied by the local receiver, although a TIPC peer may provide the message being received. Impact is denial of service via warning or kernel crash. No concrete UAF, OOB write, or information disclosure primitive is indicated by the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	DANGER TIPC IO_URING  KPANIC LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS 	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Triggered signals:

* Local unprivileged trigger: +1
  A local process can call the TIPC receive path with an oversized `buflen`, including through `io_uring` provided buffers.

* Local unprivileged high-control kernel data-plane API refinement: +1
  `io_uring` gives the local caller high control over receive buffer sizing, and the commit explicitly mentions this as a trigger path.

* Memory layout invariant restoration: +1
  The fix restores consistency between `buflen`, `dlen - offset`, and `copy` in networking receive buffer length calculation.

* Reliable kernel crash / strong DoS: +1
  The commit includes a concrete `panic_on_warn` kernel panic path through `simple_copy_to_iter()`.

Paranoid-only signal:

* Availability impact realistic: +1
  On systems with `panic_on_warn` enabled, the WARN is host-wide and can become a reliable local kernel panic. This raises the paranoid score from 4 to 5.

Not triggered:

* Remote reachable / network-triggerable: +0
  The dangerous length is supplied by the local receiver, not by a remote TIPC peer.

* Generic memory corruption: +0
  The patch shows integer truncation leading to invalid copy length and WARN/panic, but not UAF, OOB write, double-free, or type confusion.

* Privilege escalation plausible: +0
  No concrete reclaim, overwrite, information leak, or object corruption primitive is shown.

## 3. Reachability analysis

The bug is triggered by a local process using the TIPC receive path with a `buflen` larger than `INT_MAX`. The commit specifically calls out `io_uring` provided buffers as a realistic way to supply such a value.

The issue is not directly remote reachable. A remote or local TIPC peer may provide the message being received, but the security-relevant malformed length comes from the local receiver process.

Privileges are best treated as PR:L in CVSS terms and as local unprivileged for ActionableScore, assuming TIPC and `io_uring` are available to the local user. If a product disables TIPC, restricts TIPC sockets, or restricts `io_uring`, practical reachability is reduced.

Call-site confidence: high. The patch includes the affected call sites in `tipc_recvmsg()` and `tipc_recvstream()`, and the commit message shows the downstream call trace into `simple_copy_to_iter()`.

## 4. Severity interpretation

This behaves like an actionable Moderate issue, not an Important-class memory corruption vulnerability.

The demonstrated impact is local DoS via WARN and possible kernel panic when `panic_on_warn` is enabled. The bug is in a networking receive path and involves an integer conversion flaw in copy length calculation, so it deserves manual triage and should not be auto-closed purely as a low-risk warning.

However, the patch does not support treating this as privilege escalation or strong memory corruption. There is no demonstrated UAF, OOB write, controlled overwrite, type confusion, arbitrary write, or information disclosure primitive. The paranoid score is raised for reliable host-wide DoS under `panic_on_warn`, not for LPE.

## 5. One-sentence report phrase

A local integer conversion flaw in the TIPC receive path can turn an oversized `buflen` into a negative copy length, reaching `simple_copy_to_iter()` as a huge size and triggering a WARN or `panic_on_warn` kernel crash.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is not a clear privilege-escalation bug, but it is a local kernel networking receive-path integer conversion issue with a concrete panic path and `io_uring` involvement, making it an actionable Moderate candidate rather than an auto-close candidate.

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

Patch: tipc: fix integer overflow in tipc_recvmsg() and tipc_recvstream() [ Upstream
Commit: fe9bf32bb18f2d35789d4960fb007d1059bbaa38
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fe9bf32bb18f2d35789d4960fb007d1059bbaa38

Changed files:
  net/core/datagram.c
  net/tipc/socket.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=fe9bf32bb18f2d35789d4960fb007d1059bbaa38

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

The original Linux kernel CVE announcement for CVE-2026-68289 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68289

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:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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).