[CVE-2026-68480][MODERATE REGULAR] x86/bugs: Make Safe-RET robust against interrupt injection

[CVE-2026-68480][MODERATE REGULAR] x86/bugs: Make Safe-RET robust against interrupt injection

[AL-KERNEL]

CVE: CVE-2026-68480
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: x86/bugs: Make Safe-RET robust against interrupt injection
Commit: 9de1a49e8f1fbf7c372902573a27a97d4ab4d0af
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9de1a49e8f1fbf7c372902573a27a97d4ab4d0af
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68480
Analysis date: Thu, 06 Aug 2026 13:51:30 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline manual review recommended / Actionable Moderate on affected SRSO systems
Manual review required: YES

Summary:
An interrupt or exception injected during the x86 SRSO Safe-RET sequence may neutralize the mitigation and allow local speculative-execution data leakage on affected systems.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-68480 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68480

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-68480	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N';CWE-1420;*CWE-200;CWE-203;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N';BEST CVSS score: '5.5';DESCR 'The Safe-RET mitigation for SRSO on affected x86 systems can be weakened if an interrupt or exception lands inside the Safe-RET sequence after the CALL or LEA instruction. In that case the interrupted return path may resume in a state where the safe return sequence no longer provides the intended speculative execution protection, potentially allowing data leakage through a side channel. For the CVSS the PR:L is used because a local user or local process is typically needed to trigger repeated exceptions or interrupts and perform side channel measurements. The issue is not directly network reachable and does not provide an obvious write primitive or memory corruption primitive. Impact is confidentiality loss through speculative execution data exposure, with no direct evidence of integrity impact or denial of service.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / Actionable Moderate on affected SRSO systems (with actual score 3)	YES	OOB INIT LEAK DMAorINTERRUPT SPECTRE HARDWARE  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	guess

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ACTIONABLESCORE ANALYSIS
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ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline manual review recommended / Actionable Moderate on affected SRSO systems**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process can plausibly trigger exceptions or interrupts and attempt side-channel measurement.
* Confidentiality impact plausible: +1. The commit explicitly says the issue may lead to data leakage through speculative execution.
* Hard timing or speculation-dependent condition: -1. The attack depends on interrupt or exception delivery during a narrow Safe-RET sequence and on microarchitectural behavior.

Paranoid additional signal:

* Broad CPU mitigation path: +1. The affected code is in x86 entry and return-thunk mitigation logic, and impact applies to affected SRSO-capable systems with the mitigation active.

Not counted:

* No memory corruption. The patch does not show UAF, OOB write, double-free, type confusion, arbitrary write, or refcount abuse.
* No privilege escalation signal. The issue is about speculative confidentiality leakage, not direct credential or control-flow corruption.
* No remote reachability. The path is not network-triggerable by itself.

## 3. Reachability analysis

The likely attacker is a local unprivileged user able to run code, trigger exceptions or interrupts, and perform timing or speculative side-channel measurements. Namespaces or containers may not fully prevent triggering because the primitive is CPU and entry-path related, but practical leakage depends on hardware, mitigation state, scheduling, and measurement quality. The issue is only relevant on machines affected by SRSO with the Safe-RET mitigation in use.

## 4. Severity interpretation

This behaves like an actionable speculative-execution confidentiality issue, not like ordinary memory corruption or LPE. Realistic exploitation is hardware-dependent and timing-sensitive, so it does not look like a Strong Important candidate from the patch alone. However, because the affected code is in x86 mitigation logic and the stated impact is data leakage, it should not be auto-closed without checking affected CPU exposure.

## 5. One-sentence report phrase

An interrupt or exception injected during the x86 SRSO Safe-RET sequence may neutralize the mitigation and allow local speculative-execution data leakage on affected systems.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. Check affected AMD CPU models, whether SRSO and Safe-RET mitigation are active, and whether the product treats local speculative data leakage as Important or Actionable Moderate.

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

Patch: x86/bugs: Make Safe-RET robust against interrupt injection
Commit: 9de1a49e8f1fbf7c372902573a27a97d4ab4d0af
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9de1a49e8f1fbf7c372902573a27a97d4ab4d0af

Commit description:

An attacker injecting interrupts while the Safe-RET mitigation executes
on machines affected by SRSO can neutralize the safe return sequence,
potentially leading to data leakage through speculative execution.

Fixup register state as if the Safe-RET sequence executed successfully
by "emulating" it, in a manner of speaking, and avoid executing a RET
instruction after returning from the interrupt.

Co-developed-by: David Kaplan <David.Kaplan@amd.com>
Signed-off-by: David Kaplan <David.Kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  arch/x86/entry/entry_64.S
  arch/x86/include/asm/nospec-branch.h
  arch/x86/kernel/cpu/bugs.c
  arch/x86/lib/retpoline.S

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=9de1a49e8f1fbf7c372902573a27a97d4ab4d0af

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

The original Linux kernel CVE announcement for CVE-2026-68480 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68480

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:H/PR:L/UI:N/S:U/C:H/I:N/A:N
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
  The Best / paranoid CVSS score: 5.5

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: 2
  Paranoid ActionableScore: 3

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).