[CVE-2026-53094][MODERATE 7.0] bpf: Fix stale offload->prog pointer after constant blinding [ Upstream

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

CVE: CVE-2026-53094
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: bpf: Fix stale offload->prog pointer after constant blinding [ Upstream
Commit: a713b72ff88cdab4d5d692908ab1259ada511f4d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a713b72ff88cdab4d5d692908ab1259ada511f4d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53094
Analysis date: Mon, 06 Jul 2026 11:37:18 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A stale `offload->prog` pointer in the BPF dev-bound XDP path can survive constant blinding program replacement and later cause a UAF crash during network namespace cleanup, with practical exploitation gated by privileged BPF and network administration access.

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

The original Linux kernel CVE announcement for CVE-2026-53094 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53094

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-2026-53094	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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-416;*CWE-672;CWE-825;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A stale pointer use-after-free in the BPF dev-bound XDP offload path can occur after constant blinding clones a program and frees the original program while offload prog still points to the freed object. The vulnerable path is reached later during network namespace cleanup when bpf_dev_bound_netdev_unregister calls __bpf_prog_offload_destroy with the stale program pointer, which can fault in kernel context and crash the system. For the CVSS the PR:L value is used for the paranoid score because reliable triggering can be possible for a local user or service that already has delegated BPF and network administration capability in a namespace or test environment, while full host root is not necessarily required once bpf_jit_harden is enabled. The issue is not directly network reachable and cannot be triggered by packet traffic alone. Impact is at least local denial of service via kernel crash and in the paranoid case may allow confidentiality and integrity impact because this is a real UAF on a freed BPF program object.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) 	YES	BPF UAF HARDWARE LINUS TEST  INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

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

## 2. Signal breakdown

* Memory corruption, strong primitive: +2
  This is a real stale pointer UAF. `offload->prog` can point to a freed `struct bpf_prog` after constant blinding clones and replaces the program.

* Real lifetime corruption: +1
  The patch restores lifetime consistency between `aux->prog` and `offload->prog`.

* Reliable kernel crash / strong DoS: +1
  The commit shows a concrete page fault in `__bpf_prog_offload_destroy()` during `cleanup_net()`.

* Requires admin/root/CAP_* in typical deployments: -2
  Reliable triggering requires BPF/XDP program loading, dev-bound-only XDP setup, network namespace or veth setup, and `bpf_jit_harden >= 2`. In typical hardened products this is gated by root, CAP_BPF, CAP_SYS_ADMIN, CAP_NET_ADMIN, or root-controlled sysctls.

* Rare / configuration-dependent path: -1
  The issue needs dev-bound-only XDP plus constant blinding with `bpf_jit_harden >= 2`. This is not a normal packet receive path and is not directly reachable by network traffic.

* Paranoid elevation: +2 net effect
  The paranoid score keeps the issue actionable because it is a deterministic UAF in BPF object lifetime handling. However, there is no demonstrated attacker-controlled reclaim, object replacement, callback control, arbitrary write, or unprivileged trigger in the supplied patch.

## 3. Reachability analysis

The bug is triggered locally by creating a dev-bound-only XDP BPF program that goes through JIT constant blinding, then destroying the related network namespace so that `cleanup_net()` reaches the stale `offload->prog` pointer. It is not remotely network-triggerable and cannot be triggered by packets alone.

In typical deployments, this path requires privileged BPF and network administration capabilities. Namespace use can matter because the reproducer uses veth and netns, but the ability to load and attach the relevant BPF/XDP program is still normally capability-gated. If a product delegates CAP_BPF or CAP_NET_ADMIN to containers or service accounts, the practical PR may be lower than full host root, which justifies manual review.

Call-site confidence: high. The commit provides the relevant cleanup call path and the patch directly updates the stale back-pointer before freeing the replaced program.

## 4. Severity interpretation

This behaves as more than an ordinary correctness bug because it is a real UAF with a demonstrated kernel fault. Realistically, the shown impact is local DoS. Theoretical privilege escalation is not proven because the patch does not show attacker-controlled reclaim, writable stale object access, callback dispatch, type confusion, or refcount takeover.

Conservative handling is Borderline / manual review recommended. Paranoid handling is Actionable Moderate at minimum because BPF lifetime UAFs are historically sensitive and should not be auto-closed solely as DoS without checking product-specific BPF privilege exposure.

## 5. One-sentence report phrase

A stale `offload->prog` pointer in the BPF dev-bound XDP path can survive constant blinding program replacement and later cause a UAF crash during network namespace cleanup, with practical exploitation gated by privileged BPF and network administration access.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a real kernel UAF in BPF object lifetime management with a reliable crash path. Even though typical deployments require privileged BPF or network administration capabilities and no LPE primitive is demonstrated, product-specific namespace and delegated capability configurations can materially change practical exposure.

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

Patch: bpf: Fix stale offload->prog pointer after constant blinding [ Upstream
Commit: a713b72ff88cdab4d5d692908ab1259ada511f4d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a713b72ff88cdab4d5d692908ab1259ada511f4d

Changed files:
  kernel/bpf/core.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=a713b72ff88cdab4d5d692908ab1259ada511f4d

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

The original Linux kernel CVE announcement for CVE-2026-53094 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53094

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:N/I:N/A:H
  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).