[CVE-2026-46102][MODERATE 7.0] net: strparser: fix skb_head leak in strp_abort_strp()

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

CVE: CVE-2026-46102
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: strparser: fix skb_head leak in strp_abort_strp()
Commit: e9ae00490d474757c0f9c65073de83e6bb1e5a00
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e9ae00490d474757c0f9c65073de83e6bb1e5a00
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46102
Analysis date: Wed, 27 May 2026 12:26:49 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A reachable strparser-based protocol can leak partially assembled SKBs on abort or timeout, allowing repeated remote triggering to cause kernel memory exhaustion and DoS.

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

The original Linux kernel CVE announcement for CVE-2026-46102 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46102

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-2026-46102	MODERATE	CHECK	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-401;*CWE-772;**CWE-400;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 memory leak can occur in the stream parser abort path because strp_abort_strp() did not free a partially assembled skb held in strp skb_head. A peer that can repeatedly drive message assembly timeouts or aborts in a strparser based protocol may retain kernel memory and cause denial of service. For the CVSS the PR:N is used because a remote peer may trigger the affected stream input path when a strparser based service is reachable. AC:H is used because practical exploitation depends on a protocol using strparser, partial message assembly, timeout or abort behavior, and repeated triggering. The issue does not involve UAF, out of bounds write, arbitrary write, information disclosure, or privilege escalation. Impact is denial of service only through memory exhaustion.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	SIMPLEFIX LEAK SKB  INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

======================================================================
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
  `strparser` is used by network protocol consumers. If an enabled protocol exposes a strparser-based stream path, a remote peer may influence partial message assembly and abort behavior.

* Availability impact realistic: +1
  Leaked `skb_head` objects can accumulate and cause memory pressure or denial of service.

* Network protocol parser exposure: +1
  The bug is in a reusable network stream parser component rather than a purely local control path.

Subtracting signals:

* Hard or configuration-dependent trigger: -1
  Exploitation depends on a protocol using `strparser`, partial message assembly, an abort or timeout path, and repeated triggering.

Paranoid additional signal:

* Sustained remote resource exhaustion concern: +2
  If a reachable service allows repeated partial-message timeouts, a remote peer could repeatedly leak SKBs and drive stronger memory exhaustion.

No signals apply for UAF, OOB write, arbitrary write, information disclosure, privilege escalation, or direct kernel memory corruption.

## 3. Reachability analysis

The issue can be remote only when an enabled kernel protocol uses `strparser` and exposes the relevant stream parsing path to untrusted peers. A peer must repeatedly cause partial message assembly followed by abort or timeout so that `strp_abort_strp()` runs while `strp->skb_head` still holds a partially assembled SKB.

Namespaces and containers are not central. Practical exposure depends on which strparser consumers are enabled on the target and whether they are reachable from untrusted networks.

## 4. Severity interpretation

This behaves as an Actionable Moderate network resource exhaustion issue, not an Important memory corruption issue. The visible primitive is a memory leak of partially assembled SKBs.

Theoretical impact is kernel memory exhaustion and network service disruption. There is no evidence of UAF, controlled overwrite, data disclosure, or privilege escalation.

## 5. One-sentence report phrase

A reachable strparser-based protocol can leak partially assembled SKBs on abort or timeout, allowing repeated remote triggering to cause kernel memory exhaustion and DoS.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a potentially network-reachable resource exhaustion issue in a reusable stream parser. Manual review should confirm which strparser consumers are enabled and externally reachable.

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

Patch: net: strparser: fix skb_head leak in strp_abort_strp()
Commit: e9ae00490d474757c0f9c65073de83e6bb1e5a00
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e9ae00490d474757c0f9c65073de83e6bb1e5a00

Commit description:

When the stream parser is aborted, for example after a message assembly timeout,
it can still hold a reference to a partially assembled message in
strp->skb_head.

That skb is not released in strp_abort_strp(), which leaks the partially
assembled message and can be triggered repeatedly to exhaust memory.

Fix this by freeing strp->skb_head and resetting the parser state in the
abort path. Leave strp_stop() unchanged so final cleanup still happens in
strp_done() after the work and timer have been synchronized.

Fixes: 43a0c67 ("strparser: Stream parser for messages")
Cc: stable@kernel.org
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Co-developed-by: Yuan Tan <yuantan098@gmail.com>
Signed-off-by: Yuan Tan <yuantan098@gmail.com>
Suggested-by: Xin Liu <bird@lzu.edu.cn>
Tested-by: Yuan Tan <yuantan098@gmail.com>
Signed-off-by: Luxiao Xu <rakukuip@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Link: https://patch.msgid.link/ade3857a9404999ce9a1c27ec523efc896072678.1775482694.git.rakukuip@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/strparser/strparser.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=e9ae00490d474757c0f9c65073de83e6bb1e5a00

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

The original Linux kernel CVE announcement for CVE-2026-46102 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46102

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).