* [CVE-2026-89765][LOW] timers/itimer: Zero-init old itimerval before copy to userspace
@ 2026-09-12 1:08 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-12 1:08 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89765
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: timers/itimer: Zero-init old itimerval before copy to userspace
Commit: 4c66719dd1e4023c5e3f7d050f1bbefec3dfbeb4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4c66719dd1e4023c5e3f7d050f1bbefec3dfbeb4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89765
Analysis date: Fri, 11 Sep 2026 21:08:19 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89765 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89765
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: LOW
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-89765 LOW https://www.kernelcve.org/list/?q=CVE-2026-89765 CHECK WITH IMPACT FROM ORIG NN MODERATE 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:N/A:N';*CWE-200;*CWE-457;CWE-908;BEST CVSS score: '3.3';DESCR 'An information leak exists in the old getitimer() compatibility output on native sparc64 because struct __kernel_old_itimerval is stack allocated and only named fields are initialized before the whole object is copied to userspace. The implicit padding holes after tv_usec can therefore contain stale kernel stack bytes and may be exposed to a local caller. For the CVSS the PR:L is used because a local process is needed to call getitimer(), even if no special administrative capability is required. The issue is not network reachable. Impact is limited confidentiality exposure only, with no direct integrity impact, availability impact, memory corruption, or privilege escalation indicated by the code path.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES DANGER SIMPLEFIX TIMER LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::
No floor or cap changed the score.
2. Signal breakdown
Conservative signals:
* +1 Local unprivileged trigger. A normal local process can call getitimer().
* +1 Confidentiality plausible. The whole stack allocated __kernel_old_itimerval object is copied to userspace and may include uninitialized padding bytes.
* -1 Architecture specific exposure. The described layout issue is specific to native sparc64 old timeval ABI padding.
Paranoid signals:
* +1 Local unprivileged trigger. The syscall path is reachable by a local process without administrative capability.
* +1 Confidentiality plausible. The issue exposes deterministic small kernel stack padding bytes to userspace after the vulnerable copy.
Non-awarded signals:
* No Real UAF. No stale lifetime or post-free object use is established.
* No memory corruption. The primitive is read disclosure of uninitialized padding only.
* No integrity impact. No unauthorized write or state modification is shown.
* No availability impact. No crash, hang, or resource exhaustion is shown.
* No remote reachability. The trigger is local getitimer() behavior.
* No privilege escalation. The leak is small and architecture-specific, with no demonstrated exploit chain.
* No controlled reclaim, arbitrary write, OOB write, or authorization bypass is established.
3. Reachability analysis
The vulnerable path is reachable by a local process calling getitimer() through the old itimerval userspace ABI. No host administrator privilege is required. No namespace capability is relevant. There is no indication that a network packet, device input, or remote interface can trigger the copy. The main deployment limitation is that the issue depends on the native sparc64 ABI layout where __kernel_old_timeval contains padding after tv_usec. No race, special timing, sysctl, boot option, or prior privileged setup is required for the syscall path itself on affected systems.
4. Primitive and severity interpretation
The exact primitive is a small local information disclosure from uninitialized stack padding copied to userspace. The object is a stack allocated ABI structure, not an active structured kernel object with lifetime reuse. There is no cleanup or destructor stale use, no repeated release or refcount mutation, and no use-after-free. The demonstrated consequence is limited confidentiality exposure of padding holes. Stronger consequences such as privilege escalation or kernel memory corruption are speculative and not supported by the patch context. PrimitiveClass is NONE because no corruption, lifetime, ownership, authorization, or security-boundary primitive is established beyond a small information leak. ImportantCandidate is NO because the leak is narrow and does not require unresolved Important-vs-Moderate exploitation review. AutoDowngradeAllowed is YES because this is a low-severity architecture-specific info leak without memory corruption or boundary bypass.
5. One-sentence report phrase
A local getitimer() caller on native sparc64 may receive a small amount of stale kernel stack padding from struct __kernel_old_itimerval, resulting in limited confidentiality impact only.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The issue is a narrow architecture-specific information leak with no UAF, no write primitive, no DoS, no authorization bypass, and no plausible Important-class primitive from the supplied evidence.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: timers/itimer: Zero-init old itimerval before copy to userspace
Commit: 4c66719dd1e4023c5e3f7d050f1bbefec3dfbeb4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4c66719dd1e4023c5e3f7d050f1bbefec3dfbeb4
Commit description:
On native sparc64, struct __kernel_old_timeval contains a four-byte hole
after tv_usec because tv_sec is 64-bit while __kernel_suseconds_t is 32-bit.
put_itimerval() fills only the named fields in a stack-allocated
__kernel_old_itimerval and copies the entire object to userspace, so
getitimer() can expose the two padding holes.
Zero-initialize the aggregate before assigning the fields so implicit
padding is deterministic before it crosses the user/kernel boundary.
Signed-off-by: Jérémy Jean <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Assisted-by: Codex:gpt-5
Cc: [email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
kernel/time/itimer.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=4c66719dd1e4023c5e3f7d050f1bbefec3dfbeb4
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89765 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89765
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: Not available
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
The Best / paranoid CVSS score: 3.3
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: 1
Paranoid ActionableScore: 2
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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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