[CVE-2026-80669][LOW] bpf: Disable xfrm_decode_session hook attachment [ Upstream

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

CVE: CVE-2026-80669
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: bpf: Disable xfrm_decode_session hook attachment [ Upstream
Commit: aa265d47308775c5501073b08133623bcb5421f9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=aa265d47308775c5501073b08133623bcb5421f9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80669
Analysis date: Fri, 28 Aug 2026 05:34:28 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A privileged or delegated BPF LSM user could attach to xfrm_decode_session and return an error through a void packet classification path, causing BUG_ON and a kernel panic, but the issue is not directly network reachable and does not show memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-80669 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80669

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-80669	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	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-617;CWE-754;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 BPF LSM program could attach to xfrm_decode_session even though this hook can return an error and is called from security_skb_classify_flow through a void path that may hit BUG_ON when an error is returned. A local attacker able to load and attach BPF LSM programs could make packet classification reach the failing hook result and panic the kernel. For the CVSS the PR:L is used in the paranoid score because some deployments may delegate BPF capabilities or run service accounts with enough BPF privileges without full administrator control. The issue is not directly network reachable by an unauthenticated remote host because the malicious BPF LSM program must already be installed locally. Network packets may only act as the runtime trigger after local attachment. Impact is denial of service via kernel panic with no supported memory corruption or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	BPF SIMPLEFIX LINUS PACKET  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1
  The commit explicitly says a BPF LSM program can turn packet classification into a full panic through BUG_ON().
* Requires admin/root/CAP_* in typical deployments: -2
  Loading and attaching BPF LSM programs normally requires privileged BPF capabilities or root-controlled configuration. Unprivileged BPF should not be assumed.
* Availability impact realistic: +1
  The failure mode is a kernel panic, not just a warning.

Conservative total: 1

Paranoid adjustment:

* Reduced privilege or delegated BPF capability model: +1 relative to conservative
  If a service account, container root, or delegated BPF-capable process can attach BPF LSM programs without full host-root equivalence, the practical privilege requirement is closer to PR:L than PR:H.

Paranoid total: 2

Not awarded:

* Remote reachable / network-triggerable: +0
  A remote packet may trigger the path only after a malicious local BPF LSM program has already been attached.
* Generic memory corruption: +0
  The patch shows BUG_ON panic from an error-return mismatch, not UAF, OOB write, double-free, type confusion, or arbitrary write.
* Privilege escalation plausible: +0
  No LPE primitive is supported by the patch.
* Local unprivileged high-control BPF API: +0
  The affected configuration assumes BPF is privileged.

## 3. Reachability analysis

The bug is triggerable by a local actor who can load and attach BPF LSM programs to the xfrm_decode_session hook. In typical deployments this requires CAP_BPF, CAP_SYS_ADMIN, CAP_NET_ADMIN, or equivalent root-controlled BPF configuration, so conservative scoring treats it as privileged local DoS.

Namespaces and containers matter only if BPF LSM attachment is delegated to a reduced-privilege environment. In that case the practical risk rises slightly, but the primitive remains kernel panic only.

The affected path also depends on CONFIG_SECURITY_NETWORK_XFRM and BPF LSM availability. It is not directly reachable by an unauthenticated network attacker.

## 4. Severity interpretation

This behaves like an ordinary Moderate / Low-like privileged local DoS issue. The failure is severe in effect because it can panic the kernel, but the required ability to attach a BPF LSM program is normally highly privileged.

There is no supported evidence of memory corruption, information disclosure, integrity impact, or privilege escalation. Theoretical escalation should not be inferred from BUG_ON alone.

## 5. One-sentence report phrase

A privileged or delegated BPF LSM user could attach to xfrm_decode_session and return an error through a void packet classification path, causing BUG_ON and a kernel panic, but the issue is not directly network reachable and does not show memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the patch disables an invalid BPF LSM hook attachment and the demonstrated consequence is privileged local kernel panic only, with no UAF, OOB access, arbitrary write, object lifetime bug, or security-boundary bypass.

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

Patch: bpf: Disable xfrm_decode_session hook attachment [ Upstream
Commit: aa265d47308775c5501073b08133623bcb5421f9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=aa265d47308775c5501073b08133623bcb5421f9

Changed files:
  kernel/bpf/bpf_lsm.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=aa265d47308775c5501073b08133623bcb5421f9

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

The original Linux kernel CVE announcement for CVE-2026-80669 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80669

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: 1
  Paranoid ActionableScore: 2

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).