* [CVE-2026-98233][LOW] net/packet: clear RX owner on VNET header error
@ 2026-10-09 15:30 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-09 15:30 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98233
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net/packet: clear RX owner on VNET header error
Commit: bb10a0084c03a94364aeec542beddc5d49b59f59
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bb10a0084c03a94364aeec542beddc5d49b59f59
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98233
Analysis date: Fri, 09 Oct 2026 11:30:25 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98233 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98233
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: LOW
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-98233 LOW https://www.kernelcve.org/list/?q=CVE-2026-98233 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE AEGIS_AS=0 LEGACY=LOW RESULT=DIFF (independent Legacy and Aegis differ; FINAL: LOW, Aegis: 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:L';CWE-404;*CWE-772;CWE-754;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '3.7';DESCR 'An error while converting a virtio net header in tpacket_rcv can leave a TPACKET_V1 or TPACKET_V2 RX ring slot permanently marked as owned by the kernel. A one frame TPACKET_V2 ring can therefore lose its only available slot after an unsupported UDP GSO packet and subsequently drop valid packets. The demonstrated impact is limited to packet reception through the affected AF_PACKET socket and does not show a kernel crash, memory corruption, information disclosure, or privilege escalation. For the CVSS the PR:N value is used for the paranoid network interpretation because an external sender may only need network reachability to an interface monitored by a suitably configured packet socket. Reliable triggering still depends on GRO or GSO behavior, VNET header processing, ring configuration, and the ability to produce an skb with an unsupported GSO type. The practical exposure is more likely on local, virtualized, container, or data center networks than on systems without AF_PACKET VNET monitoring.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE REMOTE INIT SIMPLEFIX RACE ERRORPATH PACKET - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Concrete persistent kernel resource retention. The failed VNET header conversion leaves an RX ring slot claimed in rx_owner_map and unavailable to normal packet reception.
* No reliable kernel crash point. The demonstrated consequence is packet loss within the affected AF_PACKET ring.
* No additional Availability point. Loss of the ring slot is the same consequence already represented by the resource-retention signal.
* No remote-reachability point. External influence is plausible, but the evidence does not establish that ordinary wire traffic reliably reaches the unsupported UDP GSO condition without a preconfigured AF_PACKET VNET ring and suitable GRO or GSO behavior.
* No common-networking-path point. AF_PACKET reception is established, but this specific VNET header and TPACKET configuration is not shown to be broadly exercised.
* No UAF, OOB read, OOB write, arbitrary write, controlled reclaim, information disclosure, or authorization bypass is established.
* B5-R does not apply. There is no confirmed heap OOB write, retry-accumulated offset, or later consumption of corrupted heap state.
3. Reachability analysis
The affected socket must use a TPACKET_V1 or TPACKET_V2 RX ring with VNET header processing. Creating and configuring AF_PACKET sockets commonly involves CAP_NET_RAW, but the supplied evidence does not resolve whether the complete relevant setup is host-admin-equivalent, delegated, or fully namespace-scoped.
A network sender might influence packets observed by an already configured monitoring socket. However, it is not established that the sender can reliably cause an unsupported UDP GSO skb at this exact receive path. GRO or GSO behavior, interface configuration, and prior socket setup are prerequisites. There is no race and no special hardware requirement.
4. Primitive and severity interpretation
The exact defect is a stale logical ownership bit. On VNET header conversion failure, the kernel fails to release the claimed V1 or V2 ring slot. Later packet reception observes the slot as unavailable and drops packets.
This is CLASS_C invalid-state and localized availability behavior. It is not a memory-lifetime violation and does not modify memory outside the intended bitmap. The demonstrated impact is confined to packet reception through the affected ring, with no kernel crash or host-wide resource exhaustion.
ImportantCandidate is NO because no Important-preserving corruption or boundary primitive exists. AutoDowngradeAllowed is YES because the behavior is constrained, non-corrupting, and limited to socket-level packet loss.
5. One-sentence report phrase
A failed VNET header conversion can leave a TPACKET_V1 or TPACKET_V2 RX slot claimed, causing subsequent packet loss in the affected AF_PACKET ring without demonstrated memory corruption or host-wide denial of service.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Confirm whether remote traffic can reliably produce the required unsupported UDP GSO skb in the target deployment and whether the affected AF_PACKET socket performs security-sensitive monitoring.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: net/packet: clear RX owner on VNET header error
Commit: bb10a0084c03a94364aeec542beddc5d49b59f59
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bb10a0084c03a94364aeec542beddc5d49b59f59
Commit description:
Commit 61fad68 ("net/packet: tpacket_rcv: avoid a producer race
condition") added rx_owner_map and made tpacket_rcv() claim a V1 or V2
ring slot before converting the virtio-net header. If the conversion
fails, the drop path leaves the slot claimed.
With a one-frame TPACKET_V2 ring, an unsupported UDP GSO packet leaves
the only slot unavailable, so the ring also drops the next valid packet.
Clear the ownership bit on this error path. TPACKET_V3 already clears
its block state here.
Fixes: 61fad68 ("net/packet: tpacket_rcv: avoid a producer race condition")
Cc: [email protected]
Signed-off-by: Mark Amirkan <[email protected]>
Reviewed-by: Willem de Bruijn <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
net/packet/af_packet.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=bb10a0084c03a94364aeec542beddc5d49b59f59
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98233 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98233
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: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:L
The Best / paranoid CVSS score: 3.7
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: unknown
Paranoid ActionableScore: 1
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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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