[CVE-2026-46253][MODERATE 7.0] pstore/ram: fix buffer overflow in persistent_ram_save_old() [ Upstream

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

CVE: CVE-2026-46253
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: pstore/ram: fix buffer overflow in persistent_ram_save_old() [ Upstream
Commit: 58bda5a1d1ee98254383ef34f76b2c35140513ea
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=58bda5a1d1ee98254383ef34f76b2c35140513ea
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46253
Analysis date: Wed, 03 Jun 2026 15:05:31 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A heap OOB write and later OOB read in pstore/ram can occur when `persistent_ram_save_old()` reuses an old smaller `old_log` allocation after the persistent RAM buffer size grows, causing memory corruption under rare ramoops and timer-driven pstore update conditions.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-46253 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46253

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-46253	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-125;CWE-122;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A heap OOB write in pstore/ram can occur when persistent_ram_save_old() is called again for the same persistent_ram_zone after the persistent RAM buffer size has grown across boot or crash collection cycles. The old_log buffer may still have the earlier smaller allocation while old_log_size is updated to the newer larger size, so memcpy_fromio can copy past the end of the heap buffer and a later ramoops_pstore_read can perform an OOB read using the larger size. For the CVSS the PR:L value is used in the paranoid vector because an unprivileged local process may be able to reach the affected pstore read or timer paths on a system where ramoops and periodic pstore updates are already enabled, although reliable triggering still requires unusual crash timing and a survivable non-fatal oops. The issue is not network reachable. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to heap memory corruption. For the paranoid score, choose the highest still defensible interpretation supported by the bug class and patch context, with preference for manual-review sensitivity over autoclosed false negatives.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 4) 	MAYBE	WRITE KASAN OOB DISK INIT KERNEL_PANIC_PLUS_UAF TIMER  DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Paranoid score signals:

* Local unprivileged trigger: +1
  Possible only in a favorable configuration where ramoops and periodic pstore updates are enabled and a local user can influence the relevant read or survivable-oops path.

* Constrained kernel buffer overwrite: +1
  `memcpy_fromio()` can copy more bytes than the existing `old_log` allocation can hold. The overwrite is real, but payload and target control appear constrained.

* Weak LPE concern: +1
  Heap OOB write plus later OOB read creates memory corruption risk, but the patch does not show a reliable reclaim, object confusion, or arbitrary write primitive.

* Reliable kernel crash / strong DoS if triggered: +1
  KASAN reports slab OOB access, and a real trigger can plausibly crash the kernel.

* Confidentiality impact plausible: +1
  The later OOB read through `ramoops_pstore_read()` may expose adjacent heap data if the pstore record is readable.

* Integrity impact plausible: +1
  The heap OOB write can corrupt adjacent kernel heap memory.

* Privileged kernel/device-management memory corruption path: +1
  The corruption occurs inside trusted pstore/ram crash persistence handling.

Negative signals:

* Hard or unreliable special conditions: -1
  The required sequence is extremely narrow: prior short crash record, reboot, enabled `pstore_update_ms`, survivable non-fatal oops, timer-driven reread, and larger later buffer.

* Rare and difficult-to-reach configuration: -1
  `pstore_update_ms >= 0` is disabled by default, and ramoops must be configured.

Conservative interpretation additionally treats reliable triggering as typically requiring admin-level control over crash/pstore conditions, which lowers the practical score to 3.

## 3. Reachability analysis

The bug is local, not network reachable. In typical deployments, triggering requires ramoops to be configured, pstore periodic updates to be enabled, and a rare sequence across crash or oops handling. A normal local user usually cannot reliably create the needed pstore state or survivable kernel oops, so conservative reachability is privileged or highly environment-dependent. In a paranoid interpretation, if an unprivileged local process can reach pstore read paths and can indirectly provoke survivable oops behavior on a system where ramoops is already enabled, PR:L is defensible for triage sensitivity.

Namespaces and containers do not obviously make this broadly reachable by default. Container access to pstore is normally restricted, but misconfigured systems or delegated debugging environments could lower the practical privilege barrier.

## 4. Severity interpretation

This is not an ordinary low-risk cleanup because the patch fixes a real heap OOB write and subsequent OOB read. However, it is also not a strong Important issue by default because the trigger conditions are unusually complex and the overwrite appears constrained by pstore/ram buffer contents rather than attacker-selected heap target and payload.

Realistic behavior is closer to Borderline or Actionable Moderate. The paranoid score should not be auto-closed because memory corruption exists and confidentiality or integrity impact is plausible enough for manual review.

## 5. One-sentence report phrase

A heap OOB write and later OOB read in pstore/ram can occur when `persistent_ram_save_old()` reuses an old smaller `old_log` allocation after the persistent RAM buffer size grows, causing memory corruption under rare ramoops and timer-driven pstore update conditions.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: explicit heap OOB write plus OOB read memory corruption is present, even though the practical trigger is rare and difficult.

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

Patch: pstore/ram: fix buffer overflow in persistent_ram_save_old() [ Upstream
Commit: 58bda5a1d1ee98254383ef34f76b2c35140513ea
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=58bda5a1d1ee98254383ef34f76b2c35140513ea

Changed files:
  fs/pstore/ram_core.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=58bda5a1d1ee98254383ef34f76b2c35140513ea

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

The original Linux kernel CVE announcement for CVE-2026-46253 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46253

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:H/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

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).