[CVE-2026-64548][MODERATE 7.0] bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data() [ Upstream

[CVE-2026-64548][MODERATE 7.0] bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-64548
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data() [ Upstream
Commit: f1644c9508d24f50dd9e8ebe8d3ba86e0996d2f5
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f1644c9508d24f50dd9e8ebe8d3ba86e0996d2f5
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64548
Analysis date: Mon, 27 Jul 2026 22:31:57 -0400
ActionableScore: 6
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
An integer overflow in bpf_msg_push_data() can wrap copy + len to a small allocation size and cause an out-of-bounds memcpy in kernel memory, making this a BPF-gated local memory corruption issue with DoS demonstrated and LPE potential requiring manual review.

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

The original Linux kernel CVE announcement for CVE-2026-64548 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64548

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: 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
======================================================================

CVE-2026-64548	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:H/I:H/A:H';CWE-190;CWE-680;*CWE-787;CWE-122;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H';BEST CVSS score: '7.8';DESCR 'An integer overflow in bpf_msg_push_data() can make copy and len wrap to a small allocation size when the scatterlist ring is full or nearly full. The helper can then perform an out-of-bounds memcpy into an undersized kernel allocation, which is a concrete memory corruption primitive rather than a DoS-only condition. For the CVSS the PR:L is used for the paranoid score because BPF and sockmap access may be available to a local low privileged user in some deployments through delegated CAP_BPF, CAP_NET_ADMIN, container root, service accounts, or unprivileged BPF configurations. The issue is local and is not directly network reachable because the attacker must control the BPF helper arguments or the local program path that invokes them. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality, integrity, and availability impact due to kernel memory corruption. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	REMOTE WRITE KASAN OOB BPF  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	NO	NO	checked

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

ActionableScore=6
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 6
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Generic memory corruption, strong corruption primitive: +2. The patch fixes a u32 overflow in copy + len that can cause undersized allocation followed by out-of-bounds memcpy.
* Privilege escalation plausible: +2. Heap/OOB write in kernel memory is a plausible LPE class, even though no reliable exploit primitive is demonstrated.
* Memory layout invariant restoration: +1. The fix restores consistency between allocation size and later copy length.
* Reliable kernel crash / strong DoS: +1. The commit includes a KASAN/Oops trace from __asan_memcpy.
* Requires admin/root/CAP_* in typical deployments: -2. Loading and attaching the relevant BPF sockmap/sk_msg program usually requires CAP_BPF, CAP_NET_ADMIN, CAP_SYS_ADMIN, or root-controlled BPF configuration.

Conservative total: 4.

Paranoid interpretation:

* Treat BPF/sockmap access as PR:L if available to container root, delegated CAP_BPF/CAP_NET_ADMIN, service accounts, or systems with unprivileged BPF enabled.
* Add local low-privilege reachability and high-control BPF data-plane relevance, but apply the BPF gating cap.
* Paranoid score is capped at 6 because the issue is BPF-gated and there is no demonstrated unprivileged exploit, arbitrary write, or working LPE.

## 3. Reachability analysis

The bug is local, not directly network reachable. The attacker must control a BPF sk_msg/sockmap program path that calls bpf_msg_push_data() with a crafted len while the scatterlist ring is full or nearly full.

In typical hardened/product configurations, this requires privileged BPF access and should be treated as PR:H or privileged local. In less restrictive deployments, delegated BPF/network capabilities, container root with relevant capabilities, or unprivileged BPF settings may reduce this to PR:L.

The affected path is not a generic packet receive path. Network traffic may help exercise the sendmsg path, but the key attacker control is through the BPF helper arguments and program attachment.

Call-site confidence: high. The commit provides the helper, the overflow site, and a concrete call trace through sk_psock_msg_verdict(), tcp_bpf_sendmsg(), and sendto().

## 4. Severity interpretation

This is not an ordinary Moderate DoS-only issue. The patch describes a concrete integer overflow leading to undersized allocation and out-of-bounds memcpy, which is a real kernel memory corruption primitive.

Realistic exploitation is limited by BPF privilege gating, so the conservative score remains below Important. However, because the corruption primitive is concrete and BPF reachability can vary significantly across deployments, it should be treated as Actionable Moderate at minimum and an Important candidate under PR:L assumptions.

Theoretical impact includes privilege escalation due to kernel heap corruption. Realistic evidence currently demonstrates crash/Oops, not a working LPE.

## 5. One-sentence report phrase

An integer overflow in bpf_msg_push_data() can wrap copy + len to a small allocation size and cause an out-of-bounds memcpy in kernel memory, making this a BPF-gated local memory corruption issue with DoS demonstrated and LPE potential requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch shows a concrete kernel OOB memcpy primitive, and although typical BPF privilege gating lowers practical exposure, the bug class is memory corruption with plausible privilege-escalation relevance.

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

Patch: bpf, sockmap: reject overflowing copy + len in bpf_msg_push_data() [ Upstream
Commit: f1644c9508d24f50dd9e8ebe8d3ba86e0996d2f5
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f1644c9508d24f50dd9e8ebe8d3ba86e0996d2f5

Changed files:
  mm/kasan/shadow.c
  net/core/filter.c
  net/core/skmsg.c
  net/ipv4/tcp_bpf.c
  net/socket.c
  arch/x86/entry/syscall_64.c
  arch/x86/entry/entry_64.S

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=f1644c9508d24f50dd9e8ebe8d3ba86e0996d2f5

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

The original Linux kernel CVE announcement for CVE-2026-64548 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64548

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:H/I:H/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 4
  Paranoid ActionableScore: 6

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).