From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46182][MODERATE REGULAR] pseries/papr-hvpipe: Prevent kernel stack memory leak to userspace Date: Thu, 28 May 2026 10:33:26 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46182 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: 0479b6e9f999cc1cbad7d9f09f574fc387e605d5 List-Id: CVE: CVE-2026-46182 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: pseries/papr-hvpipe: Prevent kernel stack memory leak to userspace Commit: 0479b6e9f999cc1cbad7d9f09f574fc387e605d5 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0479b6e9f999cc1cbad7d9f09f574fc387e605d5 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46182 Analysis date: Thu, 28 May 2026 10:33:26 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: `papr_hvpipe_handle_read()` could copy uninitialized padding bytes from a stack allocated `papr_hvpipe_hdr` to userspace, causing a local kernel stack information disclosure. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46182 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46182 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. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-46182 MODERATE CHECK 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-457;*CWE-200;CWE-908;CWE-665;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '5.5';DESCR 'papr hvpipe read path copied a stack allocated papr_hvpipe_hdr to userspace after only initializing version and flags. Reserved padding bytes could contain uninitialized kernel stack data and be exposed to a local reader of the hvpipe interface. For the CVSS the PR:L is used for the paranoid score because a reduced privilege user or service with read access to the device can trigger the leak without full host administrative privileges. The issue is not network reachable. Impact is information disclosure only, with no supported memory corruption, arbitrary write, or direct privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3) MAYBE SIMPLEFIX LEAK HARDWARE LINUS INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Borderline, manual review recommended**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. A local user or service with read access to the PAPR hvpipe interface can trigger the copy to userspace. * Confidentiality impact plausible: +1. Reserved padding bytes in a stack allocated header can expose uninitialized kernel stack data. Paranoid additional signal: * Repeated stack info leak concern: +1. If the interface is repeatedly readable by a reduced privilege user, leaked stack bytes may include useful kernel pointers or sensitive transient data. Limiting factors: * No memory corruption. * No write primitive. * No UAF, double free, OOB write, or arbitrary write. * No network reachability. * Platform specific to powerpc pseries PAPR hvpipe. ## 3. Reachability analysis The issue is local and depends on access to the PAPR hvpipe read interface. It is not remotely network reachable. Namespaces and containers matter only if this platform-specific interface is delegated into a container or exposed to reduced privilege services. In normal deployments, access control around the device or file interface determines whether this is a practical unprivileged leak. ## 4. Severity interpretation This behaves like a borderline Moderate information disclosure issue. The realistic impact is leakage of a small, fixed amount of uninitialized kernel stack data through `copy_to_user()`. It does not behave like an Important memory corruption issue. There is no evidence of privilege escalation, arbitrary write, or kernel object lifetime corruption. ## 5. One-sentence report phrase `papr_hvpipe_handle_read()` could copy uninitialized padding bytes from a stack allocated `papr_hvpipe_hdr` to userspace, causing a local kernel stack information disclosure. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Review is recommended to confirm permissions on the hvpipe interface and whether untrusted users can repeatedly read it. If access is strictly privileged, this can likely be treated as low-priority information disclosure. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: pseries/papr-hvpipe: Prevent kernel stack memory leak to userspace Commit: 0479b6e9f999cc1cbad7d9f09f574fc387e605d5 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0479b6e9f999cc1cbad7d9f09f574fc387e605d5 Commit description: The hdr variable is allocated on the stack and only hdr.version and hdr.flags are initialized explicitly. Because the struct papr_hvpipe_hdr contains reserved padding bytes (reserved[3] and reserved2[40]), these could leak the uninitialized bytes to userspace after copy_to_user(). This patch fixes that by initializing the whole struct to 0. Cc: stable@vger.kernel.org Fixes: cebdb52 ("powerpc/pseries: Receive payload with ibm,receive-hvpipe-msg RTAS") Signed-off-by: Ritesh Harjani (IBM) Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/7bfe03b65a282c856ed8182d1871bb973c0b78f2.1777606826.git.ritesh.list@gmail.com Signed-off-by: Greg Kroah-Hartman Changed files: arch/powerpc/platforms/pseries/papr-hvpipe.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=0479b6e9f999cc1cbad7d9f09f574fc387e605d5 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46182 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46182 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:L/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).