From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74716][MODERATE REGULAR] accel/amdxdna: Fix locally exploitable BUG_ON in amdxdna_insert_pages() [ Upstream Date: Sat, 22 Aug 2026 17:04:07 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74716 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: 13339132d89d00b513dff0730bff3a313b9b13b5 List-Id: CVE: CVE-2026-74716 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: accel/amdxdna: Fix locally exploitable BUG_ON in amdxdna_insert_pages() [ Upstream Commit: 13339132d89d00b513dff0730bff3a313b9b13b5 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=13339132d89d00b513dff0730bff3a313b9b13b5 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74716 Analysis date: Sat, 22 Aug 2026 17:04:07 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Ordinary Moderate / Borderline manual review Manual review required: NO Summary: A local unprivileged process with access to the amdxdna device node can trigger a predictable BUG_ON through the GEM mmap fault path after MADV_DONTNEED, causing a kernel denial of service without evidence of memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74716 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74716 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-74716 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:N/I:N/A:H';CWE-617;CWE-754;CWE-703;BEST CVSS score: '5.5';DESCR 'A locally reachable BUG_ON can be triggered in the amdxdna GEM mmap path when amdxdna_insert_pages() maps a non imported GEM object with VM_MIXEDMAP and normal system memory backing. A local userspace process can mmap the object, call madvise(MADV_DONTNEED), and then access the mapping again so the shmem fault path reaches vmf_insert_pfn() with a valid PFN and a VM_MIXEDMAP VMA. This predictably hits the kernel assertion and can crash the system, resulting in denial of service. For the CVSS the PR:L is used because a local user or process must be able to access the amdxdna DRM or accel device node and create the affected mapping. The issue is not network reachable. Impact is availability loss only because the patch context shows a reachable assertion rather than UAF, OOB access, or an arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Borderline manual review (with actual score 3) SKIP CVE-2026-74716 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE READ SIMPLEFIX DMAorINTERRUPT MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Ordinary Moderate / Borderline manual review** ## 2. Signal breakdown * Local unprivileged trigger: +1 The commit explicitly states that an unprivileged userspace process can mmap a non imported GEM object, call MADV_DONTNEED, and access the mapping again. * Reliable kernel crash / strong DoS: +1 The path predictably reaches an explicit BUG_ON in vmf_insert_pfn_prot when VM_MIXEDMAP is set and pfn_valid(pfn) is true. * Availability impact realistic: +1 in paranoid score only The crash appears reliable on affected systems exposing the amdxdna device node, but this mostly overlaps with the BUG_ON DoS signal. * Rare AND hardware dependent exposure: -1 in conservative score The affected path requires AMD XDNA accel hardware and the amdxdna driver/device node to be present and accessible. No memory corruption, UAF, OOB write, arbitrary write, refcount takeover, callback control, or page-cache ownership bypass is supported by the patch. ## 3. Reachability analysis A local userspace process with access to the amdxdna DRM/accel device node can trigger the bug. This is PR:L in CVSS-like terms because local code execution and device-node access are required, but root or CAP_SYS_ADMIN is not implied by the commit. Namespaces or containers matter only if the device node is passed through to the container. The path is not network reachable. Exposure is limited to systems with the affected AMD XDNA accelerator driver and accessible device nodes. Call-site confidence: high. The commit message describes the concrete mmap, MADV_DONTNEED, fault, vmf_insert_pfn, and BUG_ON path. ## 4. Severity interpretation This behaves like an ordinary Moderate local denial-of-service issue rather than an Important-class vulnerability. The theoretical impact is a kernel crash through a reachable assertion. Realistic exploitation evidence supports availability impact only. There is no supported privilege escalation primitive and no evidence of confidentiality or integrity impact. ## 5. One-sentence report phrase A local unprivileged process with access to the amdxdna device node can trigger a predictable BUG_ON through the GEM mmap fault path after MADV_DONTNEED, causing a kernel denial of service without evidence of memory corruption or privilege escalation. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: this is a locally exploitable kernel BUG_ON with reliable DoS on affected hardware, but the patch supports availability impact only and does not show a memory corruption or privilege escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: accel/amdxdna: Fix locally exploitable BUG_ON in amdxdna_insert_pages() [ Upstream Commit: 13339132d89d00b513dff0730bff3a313b9b13b5 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=13339132d89d00b513dff0730bff3a313b9b13b5 Changed files: drivers/accel/amdxdna/amdxdna_gem.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=13339132d89d00b513dff0730bff3a313b9b13b5 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74716 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74716 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:N/I:N/A:H 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).