[CVE-2026-64411][MODERATE REGULAR] netfilter: ebtables: terminate table name before find_table_lock()

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

CVE: CVE-2026-64411
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: netfilter: ebtables: terminate table name before find_table_lock()
Commit: 4c046ca4e35a83ea32f6e748f54139f5fe2a1d01
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4c046ca4e35a83ea32f6e748f54139f5fe2a1d01
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64411
Analysis date: Sat, 25 Jul 2026 11:19:17 -0400
ActionableScore: 3
ActionableScore lower bound: 1
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
An unterminated ebtables table name can cause `request_module()` formatting to read past a stack buffer on a lookup miss, creating a local kernel stack out-of-bounds read with possible information disclosure, typically requiring CAP_NET_ADMIN but potentially reachable from delegated network namespaces.

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

The original Linux kernel CVE announcement for CVE-2026-64411 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64411

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-64411	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:L';CWE-170;CWE-126;*CWE-200;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '6.1';DESCR 'An unterminated ebtables table name can reach find_table_lock() and then request_module formatting on a lookup miss, causing vsnprintf() to read past the 32 byte name field into adjacent stack data. This is a local control plane issue through ebtables setsockopt handling, not a packet based network trigger. For the CVSS the PR:L value is used for the paranoid score because local attackers may reach the path through CAP_NET_ADMIN in a user namespace or delegated container context, even though many base systems require administrative firewall control. Impact is at least a local kernel stack out-of-bounds read. In the worst defensible case it may disclose kernel stack data through the generated module request name and may crash KASAN or hardened kernels. No write primitive is shown, so integrity impact is not assigned.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 2)	YES	READ KASAN OOB NETFILTER LINUS  INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=3
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Confidentiality impact plausible: +1. The bug is a stack out-of-bounds read in `vsnprintf()` and may read adjacent kernel stack bytes into the generated module request string.
* Broad/common subsystem exposure: +1. ebtables/netfilter code is widely available, although this is a control-plane path, not a packet-processing path.
* Requires CAP_NET_ADMIN in typical deployments: -1. The affected setsockopt path normally requires firewall administration capability, but CAP_NET_ADMIN is not always equivalent to full host root in containerized or delegated environments.

Conservative total: 1.

Paranoid additional interpretation:

* Local unprivileged trigger: +1. In systems with unprivileged user namespaces or delegated network namespaces, a local user may obtain effective CAP_NET_ADMIN for this path.
* Confidentiality impact plausible: +1. The unterminated string can over-read stack contents before hitting a NUL byte.
* Broad/common subsystem exposure: +1. netfilter/ebtables is common enough to avoid treating this as rare-only exposure.

Paranoid total: 3.

Not counted:

* No generic memory corruption score. This is read-only stack OOB, not UAF, double free, OOB write, type confusion, or arbitrary write.
* No privilege escalation score. The patch does not show reclaim, overwrite, callback control, refcount abuse, or a write primitive.
* No strong DoS score. The KASAN report demonstrates the bug, but production impact is more likely limited over-read or possible hardened-kernel failure rather than a reliably demonstrated system-wide crash.

## 3. Reachability analysis

The trigger is local through ebtables/netfilter control-plane setsockopt handling. It is not remotely reachable through packet traffic. In standard host deployments, the caller typically needs CAP_NET_ADMIN or equivalent firewall-management privileges. In containerized systems or systems with unprivileged user namespaces, the effective privilege requirement may be lower if an attacker can create or control a network namespace with ebtables access. The affected path is old and broadly present, but exploitation depends on being able to issue the relevant ebtables update operation and force a lookup miss that reaches `request_module()` formatting.

Call-site confidence: high. The commit message provides the direct call trace from `update_counters()` through `find_table_lock()`, `try_then_request_module()`, and `vsnprintf()`.

## 4. Severity interpretation

This behaves like a borderline actionable Moderate rather than an Important-class kernel vulnerability. The concrete primitive is a stack out-of-bounds read caused by missing NUL termination of a user-supplied table name. The realistic impact is possible kernel stack information disclosure through the module request formatting path, with possible crash only in KASAN or hardened configurations. There is no demonstrated write primitive, memory lifetime corruption, object replacement, or practical LPE chain.

## 5. One-sentence report phrase

An unterminated ebtables table name can cause `request_module()` formatting to read past a stack buffer on a lookup miss, creating a local kernel stack out-of-bounds read with possible information disclosure, typically requiring CAP_NET_ADMIN but potentially reachable from delegated network namespaces.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED.

This should not be auto-closed solely as a low-risk correctness fix because it has a concrete stack OOB read primitive and a plausible information-disclosure path, but it does not currently justify Important-class handling without evidence of reliable disclosure, write corruption, or LPE.

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

Patch: netfilter: ebtables: terminate table name before find_table_lock()
Commit: 4c046ca4e35a83ea32f6e748f54139f5fe2a1d01
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4c046ca4e35a83ea32f6e748f54139f5fe2a1d01

Commit description:

update_counters() and compat_update_counters() forward a user-supplied
32-byte table name to find_table_lock() without NUL-terminating it. On a
lookup miss, find_inlist_lock() calls try_then_request_module(..., "%s%s",
"ebtable_", name), and vsnprintf() reads past the name field and the
stack object until it hits a zero byte.

  BUG: KASAN: stack-out-of-bounds in string (lib/vsprintf.c:648 lib/vsprintf.c:730)
  Read of size 1 at addr ffff8880119dfb20 by task exploit/147
  Call Trace:
  ...
   string (lib/vsprintf.c:648 lib/vsprintf.c:730)
   vsnprintf (lib/vsprintf.c:2945)
   __request_module (kernel/module/kmod.c:150)
   do_update_counters.isra.0 (net/bridge/netfilter/ebtables.c:371 net/bridge/netfilter/ebtables.c:380)
   update_counters (net/bridge/netfilter/ebtables.c:1440)
   do_ebt_set_ctl (net/bridge/netfilter/ebtables.c:2573)
   nf_setsockopt (net/netfilter/nf_sockopt.c:101)
   ip_setsockopt (net/ipv4/ip_sockglue.c:1424)
   raw_setsockopt (net/ipv4/raw.c:847)
   __sys_setsockopt (net/socket.c:2393)
  ...

compat_do_replace() shares the same unterminated name via
compat_copy_ebt_replace_from_user(); terminate it there too so all
find_table_lock() callers behave alike. The other callers already
terminate the name after the copy.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Fixes: 81e675c ("netfilter: ebtables: add CONFIG_COMPAT support")
Cc: stable@vger.kernel.org
Reported-by: Weiming Shi <bestswngs@gmail.com>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Xiang Mei <xmei5@asu.edu>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  lib/vsprintf.c
  kernel/module/kmod.c
  net/bridge/netfilter/ebtables.c
  net/netfilter/nf_sockopt.c
  net/ipv4/ip_sockglue.c
  net/ipv4/raw.c
  net/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=4c046ca4e35a83ea32f6e748f54139f5fe2a1d01

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

The original Linux kernel CVE announcement for CVE-2026-64411 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64411

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:L/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:L
  The Best / paranoid CVSS score: 6.1

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: 1
  Paranoid ActionableScore: 3

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).