[CVE-2026-53337][LOW] net: bonding: fix NULL pointer dereference in bond_do_ioctl()

[CVE-2026-53337][LOW] net: bonding: fix NULL pointer dereference in bond_do_ioctl()

[AL-KERNEL]

CVE: CVE-2026-53337
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net: bonding: fix NULL pointer dereference in bond_do_ioctl()
Commit: 1b7558c85493467b2ea20738866b822db6442034
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1b7558c85493467b2ea20738866b822db6442034
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53337
Analysis date: Wed, 01 Jul 2026 10:32:32 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A local CAP_NET_ADMIN caller can trigger a NULL pointer dereference in bond_do_ioctl by passing a non existent slave interface name to bonding ioctls, causing a local denial of service but not showing memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-53337 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53337

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-2026-53337	LOW	CHECK	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-476;*CWE-20;CWE-703;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A NULL pointer dereference in bond_do_ioctl can occur because slave_dbg is called before checking whether __dev_get_by_name returned a valid slave_dev pointer. A local caller can trigger this by issuing a bonding ioctl such as SIOCBONDENSLAVE or SIOCBONDRELEASE with a non existent slave interface name, causing a kernel oops and denial of service. For the CVSS the PR:L is used for the paranoid score because CAP_NET_ADMIN may be delegated to containers, service accounts, or restricted network operators even though full bonding administration is normally privileged. The issue is not network reachable and is triggered through the local bonding control interface rather than packet traffic. Impact is denial of service only because the patch indicates a NULL pointer dereference and does not show UAF, OOB access, arbitrary write, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	NULLPTR NETWORK  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. The bug is a direct NULL pointer dereference of slave_dev->name through slave_dbg() before checking whether __dev_get_by_name() returned NULL.
* Requires admin/root/CAP_NET_ADMIN in typical deployments: -2. Triggering bonding ioctls such as SIOCBONDENSLAVE or SIOCBONDRELEASE normally requires CAP_NET_ADMIN.
* No memory corruption bonus. This is a NULL dereference, not UAF, double free, OOB write, type confusion, refcount misuse, or arbitrary write.
* No LPE bonus. The patch does not show attacker-controlled reclaim, stale object reuse, writable stale object access, callback dispatch, or object confusion.
* No confidentiality or integrity impact. The demonstrated impact is crash/oops only.

Paranoid adjustment:

* Availability impact realistic: +1 can be considered in a paranoid score because the trigger is simple once CAP_NET_ADMIN is available, and kernel oops behavior may become stronger DoS on systems with panic_on_oops.
* Privilege penalty reduced to -1 in delegated CAP_NET_ADMIN environments. Container root, service accounts, or restricted network operators may have CAP_NET_ADMIN without full host-root equivalence.

Call-site confidence: high. The vulnerable call site and the NULL check reordering are directly visible in the patch.

## 3. Reachability analysis

The bug is reachable from local userspace through the bonding ioctl control path. In normal host deployments, this requires CAP_NET_ADMIN, so it is not an unprivileged local trigger. Namespaces and containers matter because CAP_NET_ADMIN is often delegated to containers or network-management services, but the attacker still needs that capability or an equivalent management path. The issue is not network reachable and cannot be triggered by ordinary packet traffic. Bonding is common on servers, but the vulnerable path is a local administrative control-plane path, not a default remote data-plane path.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like local DoS. The realistic impact is a kernel oops or crash caused by a NULL pointer dereference. There is no evidence of UAF, OOB access, attacker-controlled overwrite, information disclosure, or privilege escalation. Theoretical escalation should not be assumed because the primitive is only a NULL dereference before validation.

## 5. One-sentence report phrase

A local CAP_NET_ADMIN caller can trigger a NULL pointer dereference in bond_do_ioctl by passing a non existent slave interface name to bonding ioctls, causing a local denial of service but not showing memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed from an actionable triage perspective because it is a straightforward CAP_NET_ADMIN-gated NULL dereference DoS with no supported memory corruption, confidentiality, integrity, or LPE primitive.

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

Patch: net: bonding: fix NULL pointer dereference in bond_do_ioctl()
Commit: 1b7558c85493467b2ea20738866b822db6442034
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1b7558c85493467b2ea20738866b822db6442034

Commit description:

In bond_do_ioctl(), slave_dev is obtained via __dev_get_by_name() which
can return NULL if the requested interface name does not exist. However,
the subsequent slave_dbg() call is placed before the NULL check:

    slave_dev = __dev_get_by_name(net, ifr->ifr_slave);
    slave_dbg(bond_dev, slave_dev, "slave_dev=%p:\n", slave_dev); //here
    if (!slave_dev)
        return -ENODEV;

The slave_dbg() macro expands to netdev_dbg(bond_dev, "(slave %s): " fmt,
(slave_dev)->name, ...) which unconditionally dereferences slave_dev->name
before the NULL check is performed. This results in a NULL pointer
dereference kernel oops when a user calls bonding ioctl (e.g.
SIOCBONDENSLAVE, SIOCBONDRELEASE, etc.) with a non-existent slave
interface name.

This is reachable from userspace via the bonding ioctl interface with
CAP_NET_ADMIN capability, making it a potential local denial-of-service
vector.

Fix by moving the slave_dbg() call after the NULL check.

Fixes: e2a7420 ("bonding/main: convert to using slave printk macros")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: ZhaoJinming <zhaojinming@uniontech.com>
Link: https://patch.msgid.link/20260601085649.4029067-1-zhaojinming@uniontech.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/bonding/bond_main.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=1b7558c85493467b2ea20738866b822db6442034

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

The original Linux kernel CVE announcement for CVE-2026-53337 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53337

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:H/UI:N/S:U/C:N/I:N/A:H
  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: 0
  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).