[CVE-2026-98801][MODERATE 7.0] net: restrict SO_RESERVE_MEM to TCP sockets and cap max value [ Upstream

[CVE-2026-98801][MODERATE 7.0] net: restrict SO_RESERVE_MEM to TCP sockets and cap max value [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98801
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: restrict SO_RESERVE_MEM to TCP sockets and cap max value [ Upstream
Commit: 492e04f9a00f3cc88a1f6899417b10f3019a624e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=492e04f9a00f3cc88a1f6899417b10f3019a624e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98801
Analysis date: Mon, 19 Oct 2026 06:08:57 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
A local unprivileged process can corrupt active socket and memcg accounting through an SO_RESERVE_MEM integer overflow or a repeatable UDP accounting race, leaving unresolved resource isolation and availability consequences.

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

The original Linux kernel CVE announcement for CVE-2026-98801 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98801

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-2026-98801	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98801 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H';CWE-362;CWE-190;CWE-682;CWE-667;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.3';DESCR 'SO_RESERVE_MEM can corrupt socket and memcg memory accounting through two related flaws. UDP receive and release paths protect sk_forward_alloc with sk_receive_queue.lock, while reservation updates use lock_sock, allowing concurrent operations to race and produce inconsistent accounting. Values near INT_MAX can also overflow sk_mem_pages(delta) and pages shifted by PAGE_SHIFT, corrupting sk_forward_alloc and sk_reserved_mem even without the UDP race. For the CVSS the PR:L value is used because a local process can create a socket and invoke setsockopt without requiring full administrative control. Remote UDP traffic may help exercise the race, but remote packets alone cannot invoke SO_RESERVE_MEM, so the issue is local rather than network reachable. The demonstrated impact is incorrect socket and memcg accounting with possible resource exhaustion or service disruption. A direct UAF, OOB access, arbitrary write, or reliable privilege escalation primitive is not established. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE to MODERATE_KPANIC because the ActionableScore threshold rule was applied. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH and INCREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN5. The independent weaker Aegis shadow evaluated CVSS 3.5 and ActionableScore 1 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	MAYBE	REMOTE PACKET  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH KPANIC INCREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=UNRESOLVED
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 4
* Raw paranoid score: 5
* Paranoid score: 5
* No floor or cap was applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +1 Local unprivileged trigger. A process can create its own socket and invoke `setsockopt(SO_RESERVE_MEM)` without host-admin-equivalent privilege.
* +1 Concrete active structured-state corruption. The UDP race corrupts `sk_forward_alloc` and memcg accounting. Large values also cause signed arithmetic overflow that corrupts `sk_forward_alloc` and `sk_reserved_mem`.
* +1 Privileged downstream consumption. Kernel reservation, release, reclaim, and UDP receive paths subsequently use these active accounting fields.
* +1 V33 trust-boundary candidate. The corrupted state participates in memcg resource accounting, leaving a credible but unresolved cgroup isolation boundary.

Paranoid additional signal:

* +1 Plausible broader availability or isolation impact. Repeated under-accounting, over-accounting, or incorrect reclaim decisions could cause resource-limit bypass or substantial memory pressure. This consequence is technically credible but not demonstrated as host-wide exhaustion.

Not awarded:

* No UAF, OOB access, arbitrary write, controlled reclaim, callback influence, or adjacent-object corruption is established.
* No direct remote-reachability points. Network traffic can participate in the UDP race, but a local `setsockopt` operation remains necessary.
* No authorization-bypass, confidentiality, LPE, or protected-resource-access points.
* No reliable kernel-crash point because the patch establishes accounting corruption, not a reproducible panic.
* No race penalty because repeated socket operations and UDP traffic can drive both sides of the race.
* NEW52 B5-R does not apply because there is no confirmed heap OOB write.
* NEW53 B3-PENDING and NEW54 B4-PENDING do not apply.

3. Reachability analysis

An ordinary local process can create TCP or UDP sockets and call `SO_RESERVE_MEM`. The oversized-value path is deterministic once a value near `INT_MAX` is accepted. The UDP path additionally requires concurrent receive or release activity, but both operations can be repeated cheaply.

Remote packets alone cannot trigger the bug because they cannot perform the required `setsockopt` call. No UID 0, capability, namespace privilege, special hardware, or prior privileged socket configuration is identified. Memory-cgroup socket accounting must be enabled for `sock_reserve_memory()` to proceed, but this is a deployment prerequisite rather than an attacker privilege.

The complete operation does not rely on a namespace-scoped capability, so `NamespaceScopedPrivilege=NO`. The unresolved boundary is whether corrupted per-socket accounting can produce undercharging, cross-cgroup pressure, or host-level exhaustion beyond the attackers own socket or memcg.

4. Primitive and severity interpretation

The primitive is corruption of active integer accounting fields inside `struct sock`. It arises through two mechanisms:

* incompatible locking between UDP receive accounting and reservation updates;
* signed overflow in page-count and byte-count calculations.

This is not an OOB write. The writes remain directed at legitimate `struct sock` fields, but the stored values are invalid and later consumed by privileged kernel memory-accounting and reclaim paths. It is therefore an active structured-state Class B candidate rather than a lifetime UAF or a strong Class A overwrite.

The demonstrated consequence is inconsistent socket and memcg accounting. Broader resource exhaustion, cgroup isolation bypass, or kernel failure remains unresolved. `ImportantCandidate=YES` follows the V33 active-state trust-boundary rule, not proof of Important severity. `AutoDowngradeAllowed=NO` preserves review of the concrete write, downstream privileged consumer, and unresolved memcg boundary.

5. One-sentence report phrase

A local unprivileged process can corrupt active socket and memcg accounting through an SO_RESERVE_MEM integer overflow or a repeatable UDP accounting race, leaving unresolved resource isolation and availability consequences.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Review whether negative or wrapped `sk_forward_alloc` and `sk_reserved_mem` values can bypass memcg charging, affect other cgroups, trigger unsafe reclaim behavior, or produce host-wide memory exhaustion.

7. Call-site confidence

Call-site confidence: medium

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

Patch: net: restrict SO_RESERVE_MEM to TCP sockets and cap max value [ Upstream
Commit: 492e04f9a00f3cc88a1f6899417b10f3019a624e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=492e04f9a00f3cc88a1f6899417b10f3019a624e

Changed files:
  net/core/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=492e04f9a00f3cc88a1f6899417b10f3019a624e

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

The original Linux kernel CVE announcement for CVE-2026-98801 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98801

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:L/UI:N/S:U/C:N/I:L/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H
  The Best / paranoid CVSS score: 5.3

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).