[CVE-2026-64113][IMPORTANT] ixgbevf: fix use-after-free in VEPA multicast source pruning

[CVE-2026-64113][IMPORTANT] ixgbevf: fix use-after-free in VEPA multicast source pruning

[AL-KERNEL]

CVE: CVE-2026-64113
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: ixgbevf: fix use-after-free in VEPA multicast source pruning
Commit: 3d931ac62411a7e43b85dba5fe45e1a4a91bd5cb
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3d931ac62411a7e43b85dba5fe45e1a4a91bd5cb
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64113
Analysis date: Sun, 19 Jul 2026 12:19:01 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A use-after-free in the ixgbevf RX NAPI path can be triggered by adjacent L2 traffic hitting the VEPA multicast source-pruning path, causing a stale freed skb pointer to be reused in the next RX iteration and potentially leading to kernel crash or memory corruption.

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

The original Linux kernel CVE announcement for CVE-2026-64113 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64113

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: IMPORTANT
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-2026-64113	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;*CWE-672;CWE-825;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'A use after free exists in the ixgbevf RX NAPI path because a freed skb pointer can survive across loop iterations after VEPA multicast source pruning. A frame whose source MAC matches the VF address can make the driver call dev_kfree_skb_irq(skb) and then continue before skb is reset to NULL. The next RX descriptor may then reuse the stale pointer and call ixgbevf_add_rx_frag on freed memory, including access to skb_shinfo(skb) and nr_frags. For the CVSS the PR:N is used for the paranoid score because an attacker does not need local privileges on the victim if they can inject suitable L2 traffic toward the affected VF. The attack is adjacent network rather than Internet remote and is most realistic in SR IOV, VEPA, or local Ethernet environments where MAC spoofed frames can reach the VF. Impact is at least denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to kernel use after free memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)	YES	REMOTE READ OOB DANGER UAF NETWORK SKB HARDWARE TEST KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=6

## 1. ActionableScore

* Conservative score: 6
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2. Trigger is packet RX path, but realistically adjacent L2 / SR IOV / VEPA reachable, not Internet remote.
* Weak LPE concern: +1. Real UAF exists, but no demonstrated reclaim, object replacement, callback control, or arbitrary write.
* Generic memory corruption, strong primitive: +2. The patch fixes a confirmed skb use-after-free after dev_kfree_skb_irq.
* Real lifetime corruption: +1. A freed skb pointer survives into the next RX loop iteration.
* Reliable kernel crash / strong DoS: +1. KASAN confirms slab-use-after-free, and RX softirq UAF can plausibly crash the host kernel.
* Common packet-processing path: +1. This is inside NIC RX processing, although limited to ixgbevf.
* Rare / difficult-to-reach configuration: -1. Requires ixgbevf VF hardware and VEPA multicast source pruning conditions.
* No demonstrated reclaim or controlled replacement: -1. The primitive is real UAF, but exploitability beyond crash is not shown.

Paranoid additions:

* Confidentiality impact plausible: +1. Kernel UAF in skb handling can sometimes become information exposure if freed memory is reused in attacker-influenced networking paths.
* Integrity impact plausible: +1. The stale skb may be passed into ixgbevf_add_rx_frag, so corruption beyond read-only dereference is technically plausible.

Availability is not double-counted separately because strong DoS is already counted.

Call-site confidence: high. The affected call path and stale pointer use are described directly in the patch context.

## 3. Reachability analysis

An attacker needs the ability to deliver suitable L2 traffic to an affected ixgbevf VF. The trigger requires a frame whose source MAC matches the VF address, causing the VEPA multicast pruning path to free the skb and continue without clearing the pointer.

This is not a general Internet-remote issue. It is most realistic in SR IOV, VEPA, local Ethernet, virtualized networking, or adjacent-network environments where MAC-spoofed or otherwise crafted frames can reach the VF. No local user account on the victim is required in that network-adjacent model, but deployment prerequisites are specific.

Namespaces and containers matter mainly if an attacker controls an adjacent VM, VF, bridge, or local L2 segment. The affected code is not a generic syscall or netlink interface.

## 4. Severity interpretation

This is stronger than an ordinary Moderate because it is a concrete skb use-after-free in a network RX path. The realistic demonstrated impact is kernel crash / DoS under specific hardware and traffic conditions.

Theoretical escalation is plausible enough for manual review because this is real kernel memory lifetime corruption, not merely a NULL dereference or warning. However, the provided patch does not show controlled reclaim, arbitrary write, function pointer control, or a reliable LPE chain, so the conservative score remains Actionable Moderate rather than automatically Important.

## 5. One-sentence report phrase

A use-after-free in the ixgbevf RX NAPI path can be triggered by adjacent L2 traffic hitting the VEPA multicast source-pruning path, causing a stale freed skb pointer to be reused in the next RX iteration and potentially leading to kernel crash or memory corruption.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is a confirmed UAF in a network packet-processing path with plausible adjacent-network triggering. Even though practical exploitation beyond DoS is not demonstrated, the bug class and skb lifetime context justify manual security review.

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

Patch: ixgbevf: fix use-after-free in VEPA multicast source pruning
Commit: 3d931ac62411a7e43b85dba5fe45e1a4a91bd5cb
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3d931ac62411a7e43b85dba5fe45e1a4a91bd5cb

Commit description:

ixgbevf_clean_rx_irq() prunes frames whose source MAC matches the VF's
own address (VEPA multicast workaround) by freeing the skb and
continuing to the next descriptor:

    dev_kfree_skb_irq(skb);
    continue;

The skb pointer is declared outside the while loop and persists across
iterations.  Because the continue skips the "skb = NULL" reset at the
bottom of the loop, the next iteration enters the "else if (skb)" path
and calls ixgbevf_add_rx_frag() on the freed skb, dereferencing
skb_shinfo(skb)->nr_frags - a use-after-free in NAPI softirq context.

The sibling driver iavf already handles this correctly by nulling the
pointer before continuing.  Apply the same pattern here.

I do not have ixgbevf hardware; the bug was found by static analysis
(scan_drop_continue_loops.py + semgrep drop_continue_in_loop, multi-tool
corroboration with the highest score in the scan).  The UAF was confirmed
under KASAN by loading a test module that reproduces the exact code
pattern (alloc skb, kfree_skb, then read skb_shinfo(skb)->nr_frags):

  BUG: KASAN: slab-use-after-free in ixgbevf_uaf_test_init+0x100/0x1000
  Read of size 8 at addr 000000006163ae78 by task insmod/30
  freed 208-byte region [000000006163adc0, 000000006163ae90)

QEMU emulates igb (82576) but not ixgbe (82599), and the igbvf VF
driver does not include the VEPA source pruning path, so a full
end-to-end reproduction with emulated hardware was not possible.

Fixes: bad1723 ("ixgbevf: Change receive model to use double buffered page based receives")
Cc: stable@vger.kernel.org
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://patch.msgid.link/20260515182419.1597859-8-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.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=3d931ac62411a7e43b85dba5fe45e1a4a91bd5cb

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

The original Linux kernel CVE announcement for CVE-2026-64113 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64113

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:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.5

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: 6
  Paranoid ActionableScore: 8

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).