[CVE-2026-74715][MODERATE 7.0] bpf: Fix netns reference imbalance in conntrack kfuncs [ Upstream

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

CVE: CVE-2026-74715
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: bpf: Fix netns reference imbalance in conntrack kfuncs [ Upstream
Commit: e5e060eb63d10b41ab60fd955649479d99b38210
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5e060eb63d10b41ab60fd955649479d99b38210
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74715
Analysis date: Sat, 22 Aug 2026 14:40:36 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in BPF conntrack kfunc option handling can imbalance network namespace references, allowing a privileged local BPF user to destroy a live namespace and trigger a kernel panic, with a plausible namespace lifetime UAF concern requiring manual review.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74715 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74715

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-2026-74715	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-362;CWE-911;*CWE-416;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'BPF conntrack kfuncs can read opts netns_id more than once while opts points to a shared BPF map value that can be modified concurrently. A racing update can make the function skip get_net_ns_by_id but later execute put_net, or can make the reverse transition leak a namespace reference. The unmatched put can destroy a live network namespace and later users may dereference invalid namespace state, causing a kernel crash and creating a plausible use-after-free lifetime hazard. For the CVSS the PR:L is selected because a local user or service with BPF related privileges is needed to load or run the affected BPF program and update the shared map value. The issue is not directly network reachable, although packet processing may exercise the already loaded BPF program. Impact is at least local denial of service via kernel panic, and the paranoid score treats the namespace lifetime corruption as a potential confidentiality and integrity risk that should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE KASAN OOB NULLPTR INIT BPF NETFILTER LEAK KERNEL_PANIC_PLUS_UAF HARDWARE LINUS  KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Memory corruption, weak or indirect corruption candidate: +1
  The bug is a race on `opts->netns_id` that can produce an unmatched `put_net()` and prematurely destroy a live network namespace. This is a real lifetime hazard, but the patch does not show attacker controlled reclaim, object replacement, overwrite, or callback control.

* Real lifetime corruption: +1
  The reference imbalance affects `struct net` lifetime management. An unmatched put can drop the final reference to a namespace that later code still expects to be valid.

* Reliable kernel crash / strong DoS: +1
  The commit includes a real kernel panic path with a general protection fault and KASAN null pointer dereference in `bpf_prog_test_run_xdp()`.

* Common networking / packet-processing related path: +1
  The affected kfuncs are BPF conntrack helpers used from networking BPF contexts such as XDP or skb paths, although setup is privileged in typical deployments.

* Hard or unreliable race / special timing required: -1
  The issue requires concurrent mutation of a shared BPF map value while the kfunc reads fields from it.

* Requires admin/root/CAP_* in typical deployments: -2
  In the evaluated configuration, unprivileged BPF is not normally available. Loading or attaching the relevant BPF program generally requires CAP_BPF, CAP_SYS_ADMIN, CAP_NET_ADMIN, or root-controlled setup.

Paranoid additions:

* Weak LPE concern / namespace lifetime corruption concern: +1
  The unmatched `put_net()` can destroy a live namespace, which is stronger than a simple NULL dereference and may create stale lifetime state. There is still no demonstrated reclaim or arbitrary write primitive, so this remains a weak concern rather than strong LPE evidence.

* Broad subsystem exposure: +1
  BPF plus netfilter conntrack is a security-sensitive and widely deployed kernel area, even if the specific trigger is gated by privileged BPF access.

## 3. Reachability analysis

The trigger is local and requires the ability to run affected BPF conntrack kfuncs and concurrently update a shared map value used as `opts`. In normal hardened product configurations, this is not reachable by an ordinary unprivileged user because unprivileged BPF is disabled or BPF loading requires elevated capabilities. Namespace or container delegation could reduce the practical privilege barrier if a container root or service account has BPF and networking capabilities, but that is configuration dependent.

The issue is not directly network reachable. Network packets may exercise an already loaded BPF program, but the attacker first needs local BPF program and map control. The race is realistic for a local actor with those privileges because shared map updates can be orchestrated from another CPU, but it is still timing dependent.

## 4. Severity interpretation

This is more than an ordinary Moderate because it is a real reference lifetime bug in a sensitive namespace object and has a demonstrated kernel panic. It is not a clear Important by conservative scoring because the affected BPF path is typically privileged and the patch does not show attacker controlled reclaim, object replacement, arbitrary write, type confusion, or a proven privilege escalation chain.

Theoretical memory corruption potential exists through premature destruction of a live `struct net`, but realistic evidence currently supports kernel crash and a plausible UAF lifetime hazard rather than a demonstrated LPE primitive. Therefore the practical bucket is Actionable Moderate at minimum, with manual review required.

## 5. One-sentence report phrase

A race in BPF conntrack kfunc option handling can imbalance network namespace references, allowing a privileged local BPF user to destroy a live namespace and trigger a kernel panic, with a plausible namespace lifetime UAF concern requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the bug is a race-driven reference imbalance on a live namespace object with a demonstrated kernel panic and plausible lifetime corruption. Even though typical BPF privilege gating prevents ordinary unprivileged reachability, the namespace lifetime impact is security-relevant enough that it should not be auto-closed.

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

Patch: bpf: Fix netns reference imbalance in conntrack kfuncs [ Upstream
Commit: e5e060eb63d10b41ab60fd955649479d99b38210
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5e060eb63d10b41ab60fd955649479d99b38210

Changed files:
  net/netfilter/nf_conntrack_bpf.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=e5e060eb63d10b41ab60fd955649479d99b38210

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

The original Linux kernel CVE announcement for CVE-2026-74715 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74715

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: 4
  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: 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).