From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46253][MODERATE 7.0] pstore/ram: fix buffer overflow in persistent_ram_save_old() [ Upstream Date: Wed, 03 Jun 2026 15:05:31 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46253 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 3 X-AL-KERNEL-Commit: 58bda5a1d1ee98254383ef34f76b2c35140513ea List-Id: 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. ====================================================================== ABOUT THIS REPORT ====================================================================== 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. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== 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 ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== 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. ====================================================================== 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 ====================================================================== 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).