[CVE-2026-80904][MODERATE REGULAR] net/tls: Fail tls_sw_splice_read() after a failed async decrypt [ Upstream

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

CVE: CVE-2026-80904
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net/tls: Fail tls_sw_splice_read() after a failed async decrypt [ Upstream
Commit: a808aadff634c7a408b2ab84d5919e9a741fdb5b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a808aadff634c7a408b2ab84d5919e9a741fdb5b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80904
Analysis date: Fri, 04 Sep 2026 18:27:39 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended / Actionable Moderate watchlist
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80904 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80904

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 REGULAR
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-2026-80904	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80904 CHECK WITH IMPACT FROM ORIG NN 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:H/A:N';CWE-354;CWE-345;CWE-755;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N';BEST CVSS score: '5.9';DESCR 'A TLS software receive path integrity handling flaw allows tls_sw_splice_read to continue delivering data after an asynchronous decrypt authentication error has broken the connection. A remote peer or a network attacker able to inject invalid TLS records can trigger the error condition, but practical exploitation depends on kTLS software RX, async decrypt behavior, and an application using splice on the TLS socket. For the CVSS the PR:N is used because no local privileges on the target are required beyond network reachability to the affected TLS endpoint. The issue is network reachable but deployment dependent. Impact is mainly integrity related because data may be consumed through splice after recvmsg and read_sock would refuse the same broken connection. There is no evidence of memory corruption, kernel privilege escalation, or direct confidentiality loss from the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended / Actionable Moderate watchlist (with actual score 4)	YES	REMOTE SIMPLEFIX SKB TEST 	YES	NO	checked

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

ActionableScore=4
ActionableScoreLower=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended / Actionable Moderate watchlist**::

2. Signal breakdown
* Remote reachable / network-triggerable: +2. A remote peer or MITM can create the failed TLS authentication condition by sending invalid TLS records, assuming the endpoint uses the affected kTLS RX path.
* Integrity impact plausible: +1. The splice read path can continue delivering records after the connection should be considered broken due to authentication failure.
* Common networking receive path, paranoid only: +1. This is in net/tls socket receive handling, but the conservative score does not count it fully because kTLS software RX plus splice plus async decrypt is deployment dependent.
* Rare AND difficult-to-reach subsystem/configuration: -1 conservative only. Practical triggering requires kTLS software RX, async decrypt behavior, and an application using splice on the TLS socket.
* No memory corruption signal. The patch shows a missing error check, not UAF, OOB write, double free, refcount takeover, or object lifetime corruption.
* No LPE signal. There is no supported path to privilege escalation from the patch context.

3. Reachability analysis
The bug can be influenced by a remote TLS peer or network attacker able to cause an authentication failure on a kTLS software receive connection. No local privileges on the target are required for the network-side trigger, so PR:N is reasonable for CVSS-style reasoning. However, the vulnerable read behavior only matters when the local application uses tls_sw_splice_read rather than recvmsg or read_sock, and when async decrypt error state is present. This is not a generic TCP packet path for all TLS applications.

4. Severity interpretation
This behaves more like an integrity-focused actionable Moderate than an Important-class kernel vulnerability. The realistic impact is that splice can consume data on a connection that other TLS read paths correctly refuse after authentication failure. Theoretical severity is bounded because there is no evidence of memory corruption, kernel crash, data disclosure, arbitrary write, or privilege escalation. Manual review is still justified because the issue is network-influenced and touches TLS authentication semantics.

5. One-sentence report phrase
A kTLS software RX logic flaw lets tls_sw_splice_read continue delivering records after an async decrypt authentication failure, making this a network-influenced integrity issue requiring kTLS RX, async decrypt behavior, and splice usage.

6. Manual review recommendation
MANUAL CHECK REQUIRED. Network-influenced TLS authentication handling bugs should not be auto-closed even without memory corruption, because application impact depends on how splice output is trusted.

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

Patch: net/tls: Fail tls_sw_splice_read() after a failed async decrypt [ Upstream
Commit: a808aadff634c7a408b2ab84d5919e9a741fdb5b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a808aadff634c7a408b2ab84d5919e9a741fdb5b

Changed files:
  net/tls/tls_sw.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=a808aadff634c7a408b2ab84d5919e9a741fdb5b

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

The original Linux kernel CVE announcement for CVE-2026-80904 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80904

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:L/A:N
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
  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: 4

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 REGULAR

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).