[CVE-2026-80663][MODERATE 7.0] tools/power/x86/intel-speed-select: Harden daemon pidfile open

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

CVE: CVE-2026-80663
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: tools/power/x86/intel-speed-select: Harden daemon pidfile open
Commit: 905493a6338c82a70da16f86e0a6215db5a3d73d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=905493a6338c82a70da16f86e0a6215db5a3d73d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80663
Analysis date: Fri, 28 Aug 2026 05:42:33 -0400
ActionableScore: 7
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A symlink-following flaw in intel-speed-select daemon pidfile handling allows a local unprivileged user to cause a root-run daemon to write pidfile data into an attacker-chosen file, creating a root-level file clobber primitive with integrity impact and possible local privilege escalation depending on deployment.

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

The original Linux kernel CVE announcement for CVE-2026-80663 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80663

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-2026-80663	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:L/I:H/A:H';CWE-59;CWE-61;CWE-377;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L';BEST CVSS score: '7.3';DESCR 'A symlink following issue exists in the intel-speed-select daemon pidfile handling because a fixed pidfile path under /tmp was opened without O_NOFOLLOW and without verifying that the opened object is a regular file. A local unprivileged user can pre create a symlink at that path and wait for a root run daemon instance to open and write the pidfile, causing root level clobbering of an attacker chosen file. For the CVSS the PR:L is used because the attacker needs local user access to create the symlink and influence the local filesystem namespace, but does not need root privileges. The issue is not network reachable and is triggered through local filesystem state during daemon startup. Impact is mainly integrity loss from root level file overwrite and possible denial of service if a sensitive system file is corrupted. In worst case this should be treated as a possible local privilege escalation candidate because root file clobbering may be exploitable depending on the exact target file and service configuration.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)  SKIP CVE-2026-80663 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	OOB LOCK INIT SIMPLEFIX KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN6 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=7
ActionableScoreLower=6

## 1. ActionableScore

Conservative score: 6
Paranoid score: 7
Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Triggered signals:

* Local unprivileged trigger: +1. A local unprivileged user can pre-create a symlink at the fixed pidfile path under /tmp.
* Weak LPE concern conservative: +1. The primitive is root-level pidfile clobbering of an attacker-chosen file, but the written content is constrained and not a fully arbitrary payload.
* Stronger LPE plausibility paranoid: +2. Root-owned arbitrary file clobbering via symlink races is a classic local privilege escalation candidate depending on the exact file target, daemon behavior, and whether truncation or predictable pid content can be abused.
* Security-boundary bypass with practical sensitive-object access: +2. The bug bypasses normal filesystem permission boundaries by causing a root-run daemon to open and write to a file selected by an unprivileged user.
* Practical exploit chain strongly implied: +1. The commit directly describes local symlink pre-creation followed by root daemon write into an attacker-chosen file.
* Integrity impact plausible: +1. The main impact is unauthorized modification or corruption of privileged files.
* Availability impact plausible: +1. Corrupting selected system files can cause local service or system disruption.
* Legacy or non-default execution mode: -1. The issue requires intel-speed-select daemon mode to be used and root daemon startup to occur.

Not triggered:

* Remote reachable: +0. No network trigger is involved.
* Generic memory corruption: +0. This is a userspace symlink-following file clobber issue, not kernel memory corruption.
* Dirty-Pipe-like page-cache or COW violation: +0. No shared page-cache ownership bypass is shown.
* Requires admin/root by attacker: 0. The attacker does not need root, but a root-run daemon instance must be started by the system or administrator.

## 3. Reachability analysis

The attacker needs local user access and write access to the relevant /tmp pidfile path before the daemon starts. The vulnerable action occurs when the intel-speed-select daemon runs as root and opens the attacker-prepared symlink without O_NOFOLLOW. Containers or namespaces matter if the daemon shares the same /tmp namespace or if a reduced-privilege service account can influence the pidfile path visible to the host-root daemon. This is not a default kernel data path and not network reachable, but the trigger is simple in affected deployments where daemon mode is used.

Call-site confidence: high. The patch shows the vulnerable open call and the added O_NOFOLLOW plus fstat and S_ISREG validation at the exact pidfile open site.

## 4. Severity interpretation

This is not ordinary Moderate like a simple local crash or resource leak. It is an actionable local file-permission bypass because an unprivileged user can cause a root process to write to an attacker-chosen path. Realistic exploitation depends on whether the constrained pidfile write can be converted into useful corruption of a sensitive file. Theoretical LPE is plausible enough for manual review, but the patch does not demonstrate an unconstrained arbitrary write or kernel memory corruption primitive. Conservative handling is Actionable Moderate, while paranoid handling is a Strong Important candidate.

## 5. One-sentence report phrase

A symlink-following flaw in intel-speed-select daemon pidfile handling allows a local unprivileged user to cause a root-run daemon to write pidfile data into an attacker-chosen file, creating a root-level file clobber primitive with integrity impact and possible local privilege escalation depending on deployment.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.

Reason: root-level attacker-chosen file clobbering is often deployment-dependent and may range from local DoS to practical privilege escalation, so it should not be auto-closed without checking the pidfile path, daemon startup model, write semantics, and realistic target files.

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

Patch: tools/power/x86/intel-speed-select: Harden daemon pidfile open
Commit: 905493a6338c82a70da16f86e0a6215db5a3d73d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=905493a6338c82a70da16f86e0a6215db5a3d73d

Commit description:

Avoid symlink-based pidfile clobbering by opening the pidfile with
O_NOFOLLOW and validating it with fstat() before locking/writing.

The daemon currently uses a fixed pidfile path under /tmp. A local
unprivileged user can pre-create a symlink at that path and cause a
root-run daemon instance to write into an attacker-chosen file.

Fixes: 7fd786d ("tools/power/x86/intel-speed-select: OOB daemon mode")
Signed-off-by: Ali Ahmet MEMIS <dev@unknownbbqr.xyz>
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  tools/power/x86/intel-speed-select/isst-daemon.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=905493a6338c82a70da16f86e0a6215db5a3d73d

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

The original Linux kernel CVE announcement for CVE-2026-80663 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80663

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:H/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H
  The Best / paranoid CVSS score: 7.3

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: 6
  Paranoid ActionableScore: 7

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).