[CVE-2026-53078][MODERATE 7.0] bpf: Fix same-register dst/src OOB read and pointer leak in sock_ops [ Upstream

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

CVE: CVE-2026-53078
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: bpf: Fix same-register dst/src OOB read and pointer leak in sock_ops [ Upstream
Commit: 18e3ffde1822f0b48b1753bf34aa97ce839df1d8
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=18e3ffde1822f0b48b1753bf34aa97ce839df1d8
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53078
Analysis date: Thu, 25 Jun 2026 13:46:31 -0400
ActionableScore: 6
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A BPF sock_ops same-register ctx access bug can leave a stale kernel ctx pointer in the destination register, allowing verifier/runtime type confusion that may cause stack OOB read, kernel pointer disclosure, or kernel crash when reachable by a local actor with BPF sock_ops attach capability.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-53078 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53078

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-2026-53078	MODERATE	CHECK	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:H';CWE-125;*CWE-200;CWE-843;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '7.1';DESCR 'A BPF sock_ops context access bug can leave a stale ctx pointer in dst_reg when dst_reg and src_reg are the same register and the fullsock or locked_tcp_sock check fails. The verifier may then treat the value as PTR_TO_SOCKET_OR_NULL or as a scalar, while the runtime value is still a kernel ctx pointer. This can allow a bogus socket pointer to reach helpers such as bpf_skc_to_tcp6_sock and can cause stack OOB read or kernel pointer disclosure. For the CVSS the PR:L is used in the paranoid score because a local actor with delegated BPF or network administration capability may be enough in practical deployments, even if many systems restrict BPF sock_ops loading to privileged administrators. The issue is not directly network reachable as an AV:N bug because the attacker must be able to load or attach a BPF sock_ops program. Impact is at least local denial of service or information disclosure, and in the worst still defensible interpretation it may expose sensitive kernel addresses or memory through a BPF verifier type confusion path.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) 	MAYBE	REMOTE WRITE OOB BPF LEAK LINUS  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	-	-	checked

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ACTIONABLESCORE ANALYSIS
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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 score:

* +1 Weak LPE concern: the stale ctx pointer can be interpreted as a socket-like object or scalar by verifier/runtime mismatch, but no arbitrary write or reclaim primitive is shown.
* +1 Memory corruption, weak/indirect corruption candidate: this is pointer confusion / bogus object interpretation, not a proven strong corruption primitive.
* +1 Reliable kernel crash / strong DoS: the bogus socket pointer can reach helpers such as `bpf_skc_to_tcp6_sock()` and cause stack OOB access.
* +1 Confidentiality impact plausible: `SOCK_OPS_GET_FIELD` can leave a kernel pointer where the verifier believes a scalar exists, creating a pointer leak.
* +1 Local high-control kernel data-plane API: BPF gives precise control over register usage and helper paths once program loading/attach is available.
* +1 Broad/common subsystem exposure: BPF and TCP sock_ops are security-sensitive kernel networking facilities.
* -2 Requires CAP_BPF/CAP_NET_ADMIN or similar privileges in typical deployments.

Paranoid score:

* Same positive signals as above.
* No `-2` full-admin penalty in the paranoid interpretation, because delegated BPF/network administration, container root, or service accounts may have enough practical access without being equivalent to full host root.

Not counted:

* Remote reachable: not counted. Network traffic may help reach request_sock / TCP_NEW_SYN_RECV states, but the attacker still needs local ability to load or attach a BPF sock_ops program.
* Strong memory corruption: not counted. The patch supports OOB read and pointer leak, but not OOB write, UAF reclaim, arbitrary write, or controlled overwrite.
* Strong LPE plausibility: not counted. LPE is a concern due to verifier pointer confusion, but a direct privilege escalation primitive is not demonstrated.

## 3. Reachability analysis

The bug is triggered by a local actor able to load and attach a BPF sock_ops program and craft ctx accesses where `dst_reg == src_reg`. In normal host deployments this usually requires privileged BPF or network administration capability, so the conservative interpretation applies a privilege penalty. In containerized or delegated environments, CAP_BPF, CAP_NET_ADMIN, cgroup BPF delegation, or reduced-capability service accounts may make the bug reachable without full host-root equivalence, which supports the paranoid score.

The path is not directly AV:N/network-triggerable. Remote TCP activity can influence socket state, but cannot exploit the issue alone without local BPF program control. The exploitability is more realistic than a pure theoretical bug because the commit explicitly describes pointer leak and stack OOB read behavior.

## 4. Severity interpretation

This is stronger than an ordinary Moderate because it involves BPF verifier/runtime state mismatch, kernel pointer disclosure, and a bogus pointer path into helpers. It is not clearly Important by itself because the demonstrated primitive is read/leak/crash oriented rather than a strong write or lifetime corruption primitive. The best practical bucket is Actionable Moderate, with Strong Important candidate handling justified for manual triage because BPF verifier confusion bugs are historically sensitive.

## 5. One-sentence report phrase

A BPF sock_ops same-register ctx access bug can leave a stale kernel ctx pointer in the destination register, allowing verifier/runtime type confusion that may cause stack OOB read, kernel pointer disclosure, or kernel crash when reachable by a local actor with BPF sock_ops attach capability.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the issue involves BPF verifier-related pointer confusion, an explicit kernel pointer leak, and an OOB read candidate. It should not be auto-closed even though the realistic trigger usually requires BPF-related privileges.

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

Patch: bpf: Fix same-register dst/src OOB read and pointer leak in sock_ops [ Upstream
Commit: 18e3ffde1822f0b48b1753bf34aa97ce839df1d8
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=18e3ffde1822f0b48b1753bf34aa97ce839df1d8

Changed files:
  net/core/filter.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=18e3ffde1822f0b48b1753bf34aa97ce839df1d8

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

The original Linux kernel CVE announcement for CVE-2026-53078 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53078

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:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
  The Best / paranoid CVSS score: 7.1

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: 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).