[CVE-2026-74268][MODERATE 7.0] tcp: clear sock_ops cb flags before force-closing a child socket [ Upstream

[CVE-2026-74268][MODERATE 7.0] tcp: clear sock_ops cb flags before force-closing a child socket [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74268
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: tcp: clear sock_ops cb flags before force-closing a child socket [ Upstream
Commit: ce311bd2e36596f0aa2c92ca86fb3e019ac57eae
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ce311bd2e36596f0aa2c92ca86fb3e019ac57eae
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74268
Analysis date: Sun, 16 Aug 2026 06:15:20 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A remote TCP peer may trigger a BPF sock_ops callback on a never-established child socket during forced close, causing tcp_call_bpf to run without the expected socket lock and potentially producing a kernel warning or crash in affected configurations.

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

The original Linux kernel CVE announcement for CVE-2026-74268 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74268

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-74268	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-667;CWE-362;CWE-703;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.9';DESCR 'A TCP child socket can inherit BPF sock_ops callback flags from the listener and then enter a forced close path if setup fails before the socket is established. In that path tcp_done can reach tcp_set_state and tcp_call_bpf without the socket lock that tcp_call_bpf expects, which triggers sock_owned_by_me warning and can become a denial of service on systems where such warnings are fatal. For the CVSS the PR:N is used because a remote peer may only need network reachability to the affected TCP listener, assuming the listener has BPF sock_ops state callbacks enabled. The issue is network reachable but only under a specific target configuration and failure path, so AC:H is appropriate. Impact is mainly availability through WARN or kernel crash. No concrete information leak or write primitive is visible from the patch, so confidentiality and integrity remain none in both base and paranoid scoring.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	REMOTE INIT BPF UAF NETWORK IPV6 	NO	NO	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:

* Remote reachable / network-triggerable: +2. A remote TCP peer can potentially hit the failed child socket setup path if the target listener already has BPF sock_ops state callbacks enabled.
* Common networking core path or packet-processing path: +1. The issue is in the TCP receive / SYN child socket creation path.
* WARN/state invariant violation concern: +1. The bug violates the expected socket lock invariant and reaches sock_owned_by_me warning through tcp_done -> tcp_set_state -> tcp_call_bpf.
* Hard or unreliable race / special timing or failure path required: -1. Triggering requires a child socket setup failure before establishment plus inherited BPF_SOCK_OPS_STATE_CB_FLAG.

Paranoid additional signals:

* Reliable kernel crash / strong DoS: +1. On systems with panic_on_warn or fatal warning policy, the remote warning can become a kernel crash.
* Availability impact realistic: +1. In the paranoid interpretation, repeated remote triggering against a configured listener can cause host-wide DoS.

Not counted:

* Generic memory corruption: +0. The patch shows no UAF, OOB write, double free, arbitrary write, or type confusion.
* Privilege escalation plausible: +0. No reclaim, callback target control, write primitive, or object replacement is demonstrated.
* Confidentiality / Integrity: +0. The visible effect is warning or crash, not disclosure or modification.

## 3. Reachability analysis

A remote TCP peer may trigger the issue if it can connect to an affected TCP listener that has inherited BPF sock_ops callback flags and if the child socket setup fails before the socket becomes established. The attacker does not need local privileges on the target for the network trigger itself, so PR:N is reasonable for CVSS under that deployment assumption.

However, the vulnerable callback state normally depends on privileged BPF configuration. Loading or attaching the relevant BPF sock_ops program is typically gated by root, CAP_BPF, CAP_NET_ADMIN, or equivalent privileged setup. This makes exposure configuration-dependent rather than universal.

Namespaces do not obviously lower the trigger requirement for the remote attacker, but they may matter for who can create the affected listener and attach BPF in a local/containerized environment. Call-site confidence: high, because the commit gives the concrete TCP call trace and the patch changes the common forced-destroy path.

## 4. Severity interpretation

This behaves more like an actionable Moderate than an Important vulnerability. The realistic demonstrated impact is DoS through WARN, and stronger DoS only applies where warnings are fatal. The issue is worth manual review because it is in a remote TCP path and can be reached without attacker privileges once a vulnerable listener configuration exists.

Theoretical memory corruption or privilege escalation is not supported by the patch. The bug is a locking/context invariant violation around BPF sock_ops callbacks on a never-established child socket, not a demonstrated lifetime corruption primitive.

## 5. One-sentence report phrase

A remote TCP peer may trigger a BPF sock_ops callback on a never-established child socket during forced close, causing tcp_call_bpf to run without the expected socket lock and potentially producing a kernel warning or crash in affected configurations.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.

Reason: the issue is network reachable in some TCP plus BPF sock_ops deployments, and the paranoid impact can reach strong DoS when WARN is fatal, but the patch does not support memory corruption or privilege escalation.

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

Patch: tcp: clear sock_ops cb flags before force-closing a child socket [ Upstream
Commit: ce311bd2e36596f0aa2c92ca86fb3e019ac57eae
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ce311bd2e36596f0aa2c92ca86fb3e019ac57eae

Changed files:
  include/net/sock.h
  net/ipv4/tcp.c
  net/ipv4/tcp_ipv4.c
  net/ipv4/tcp_minisocks.c
  include/net/tcp.h
  net/ipv4/inet_connection_sock.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=ce311bd2e36596f0aa2c92ca86fb3e019ac57eae

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

The original Linux kernel CVE announcement for CVE-2026-74268 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74268

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:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.9

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).