[CVE-2026-80675][MODERATE 7.0] libbpf: Reject non-exclusive metadata maps in the signed loader [ Upstream

[CVE-2026-80675][MODERATE 7.0] libbpf: Reject non-exclusive metadata maps in the signed loader [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80675
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: libbpf: Reject non-exclusive metadata maps in the signed loader [ Upstream
Commit: b6862b6a25c6a925fb0b0e549ee4a52a8d2966fb
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b6862b6a25c6a925fb0b0e549ee4a52a8d2966fb
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80675
Analysis date: Fri, 28 Aug 2026 05:21:49 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A TOCTOU style flaw in the libbpf signed loader can allow a non-exclusive metadata map to be modified after SHA calculation, causing stale metadata validation and a possible signed-loader policy bypass in local BPF control-plane contexts.

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

The original Linux kernel CVE announcement for CVE-2026-80675 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80675

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
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CVE-2026-80675	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-367;CWE-345;CWE-863;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:L';BEST CVSS score: '7';DESCR 'A TOCTOU style validation flaw in the libbpf signed loader can allow metadata map contents to change after map sha is calculated and before the signed loader relies on that value. This happens when the metadata map is frozen but not exclusive, so another BPF program with map access can mutate the contents and make the loader validate stale data. For the CVSS the PR:L is used because reliable triggering requires local BPF object access or a delegated BPF loading context, but not necessarily full root privileges. The issue is not network reachable and is triggered through the local BPF control plane. Impact is primarily integrity bypass of the signed loader trust model, with possible confidentiality or availability impact depending on what the accepted BPF program is allowed to observe or enforce. YES REQUIRES MANUAL CHECK.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)  SKIP CVE-2026-80675 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	BPF IMPROVEONLY  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Security-boundary bypass with practical sensitive-object access: +2
  The signed loader is an intended trust boundary. A non-exclusive metadata map can let another BPF program mutate metadata after `map->sha` was calculated, making validation rely on stale data.

* Integrity impact plausible: +1
  The main impact is bypassing signed-loader metadata integrity checks.

* Practical exploit chain strongly implied: +1
  The commit directly describes the sequence: frozen but non-exclusive map, SHA calculated by `BPF_OBJ_GET_INFO_BY_FD`, later mutation by another BPF program, stale validation passes.

* Requires privileged or delegated BPF access in typical deployments: -1
  This is not a normal unprivileged local interface in hardened product configurations. However, I use -1 rather than -2 because the issue may break a capability-separated or delegated signed-loader trust model, not merely affect full host root.

Paranoid additions:

* Confidentiality impact plausible: +1
  If the signed-loader boundary is used to restrict what BPF programs may observe, stale metadata validation could indirectly allow a program with unintended observation scope.

* Availability impact plausible: +1
  Depending on the accepted BPF program and attach context, bypassing the signed-loader policy could affect enforcement or runtime behavior, though this is secondary and not a memory-corruption crash primitive.

## 3. Reachability analysis

The bug is local and control-plane based. It requires BPF object access, a signed-loader workflow, and another BPF program or actor with access to the same non-exclusive metadata map. It is not network reachable.

In typical hardened deployments, unprivileged BPF is disabled and loading or attaching BPF programs requires `CAP_BPF`, `CAP_SYS_ADMIN`, `CAP_NET_ADMIN`, or a privileged loader service. Namespace or container delegation can lower practical privilege requirements if a container root, service account, or restricted loader context is trusted to use the signed-loader mechanism without full host-root equivalence.

The path is not a default generic kernel attack surface. It is actionable because it affects a security validation boundary, not because it gives a direct memory corruption primitive.

## 4. Severity interpretation

This behaves more like an actionable Moderate security-boundary bypass than an ordinary Moderate correctness bug. It is not a strong Important memory-corruption candidate because the patch does not show UAF, OOB write, arbitrary write, type confusion, or attacker-controlled reclaim.

The realistic impact is stale validation and integrity bypass in the libbpf signed-loader model. The paranoid score is higher because signed BPF loading is a security-sensitive mechanism and the bypass may affect confidentiality or availability depending on what the accepted BPF program can observe or enforce.

## 5. One-sentence report phrase

A TOCTOU style flaw in the libbpf signed loader can allow a non-exclusive metadata map to be modified after SHA calculation, causing stale metadata validation and a possible signed-loader policy bypass in local BPF control-plane contexts.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.
YES REQUIRES MANUAL CHECK.

Reason: this is not generic memory corruption, but it affects a signed-loader trust boundary and the practical impact depends on the product BPF privilege model, loader architecture, and whether non-root delegated BPF workflows are supported.

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

Patch: libbpf: Reject non-exclusive metadata maps in the signed loader [ Upstream
Commit: b6862b6a25c6a925fb0b0e549ee4a52a8d2966fb
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b6862b6a25c6a925fb0b0e549ee4a52a8d2966fb

Changed files:
  include/linux/bpf.h
  kernel/bpf/syscall.c
  tools/lib/bpf/gen_loader.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=b6862b6a25c6a925fb0b0e549ee4a52a8d2966fb

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

The original Linux kernel CVE announcement for CVE-2026-80675 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80675

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:H/PR:L/UI:N/S:U/C:L/I:H/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 3
  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: NO
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).