From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-63841][MODERATE REGULAR] drm/amdgpu/jpeg: set no_user_fence for JPEG v5.0.1 ring [ Upstream Date: Sun, 19 Jul 2026 11:32:32 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-63841 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: d0f6ae14c0452be4fc3aa5cf81c74e68b3243050 List-Id: CVE: CVE-2026-63841 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/amdgpu/jpeg: set no_user_fence for JPEG v5.0.1 ring [ Upstream Commit: d0f6ae14c0452be4fc3aa5cf81c74e68b3243050 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d0f6ae14c0452be4fc3aa5cf81c74e68b3243050 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63841 Analysis date: Sun, 19 Jul 2026 11:32:32 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: The amdgpu JPEG v5.0.1 ring incorrectly allowed user fence CS submissions despite lacking 64-bit user fence write support, allowing a local GPU user to trigger invalid fence handling and possible GPU or driver DoS without evidence of memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63841 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63841 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-2026-63841 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-20;CWE-754;**CWE-400;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'The amdgpu JPEG v5.0.1 ring can accept command submissions with user fences even though the ring does not support 64-bit user fence writes. A local process with access to the DRM or amdgpu command submission interface could submit such a request and trigger invalid fence handling, GPU faults, reset behavior, or a driver level denial of service. For the CVSS the PR:L is used because reliable triggering requires a local user context with access to the GPU submission interface, but does not necessarily require full administrator privileges. The issue is not network reachable and is not triggered by packet traffic. Impact is primarily denial of service. No concrete UAF, OOB write, arbitrary write, or information leak primitive is evident from the patch context, so confidentiality and integrity are not raised.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 3) SKIP CVE-2026-63841 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE SIMPLEFIX HARDWARE INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown * Local unprivileged trigger: +1 A local process with access to the DRM or amdgpu command submission interface may submit CS requests. This normally does not require full root if the user has access to the render node or GPU device node. * Availability impact realistic: +1 Unsupported user fence submissions on a JPEG ring that does not support 64-bit user fence writes can plausibly cause GPU faults, failed submissions, reset behavior, or driver-level DoS. * Reliable kernel crash / strong DoS, paranoid only: +1 Paranoid scoring assumes repeated invalid submissions may cause a stronger GPU or driver availability failure. The patch does not show a clear kernel memory corruption or host-wide panic primitive, so this is not used in the conservative score. * No generic memory corruption: +0 The patch only sets `.no_user_fence = true` to reject unsupported CS submissions. There is no evidence of UAF, double free, OOB write, arbitrary write, refcount misuse, type confusion, or page-cache corruption. * No privilege escalation signal: +0 No concrete LPE primitive is shown. Unsupported fence writes are not enough by themselves to infer attacker-controlled kernel memory corruption. * No confidentiality or integrity impact: +0 The patch does not indicate information disclosure, privileged data modification, or policy bypass. * No admin/root penalty: 0 Triggering likely requires local GPU device access, but not necessarily CAP_SYS_ADMIN or full host root. ## 3. Reachability analysis The issue is local-only and reachable through amdgpu DRM command submission on systems with affected JPEG v5.0.1 hardware. It is not network reachable and is not triggered by packet traffic. Namespaces or containers matter only if GPU device nodes are passed through to the container. In that case, a reduced-privilege container or service account with GPU access may be able to trigger the issue, but this still remains a local device-interface DoS scenario rather than a demonstrated escape or LPE. The affected path is hardware-specific. It requires an AMD GPU generation exposing the JPEG v5.0.1 ring and user access to the relevant DRM/amdgpu interface. ## 4. Severity interpretation This behaves more like ordinary Moderate or Low-like local DoS than an Important-class kernel vulnerability. The realistic impact is invalid GPU fence handling leading to failed CS, GPU reset, hang, or driver availability degradation. The theoretical concern is that unsupported 64-bit user fence writes touch a low-level GPU synchronization path, but the patch does not show attacker-controlled kernel memory corruption, object lifetime abuse, arbitrary write, or privilege escalation. Paranoid scoring reaches 3 only to avoid auto-dismissal if the evaluated product exposes GPU render nodes broadly and GPU reset/hang has operational impact. It is still not an Actionable Moderate or Important candidate based on the provided evidence. ## 5. One-sentence report phrase The amdgpu JPEG v5.0.1 ring incorrectly allowed user fence CS submissions despite lacking 64-bit user fence write support, allowing a local GPU user to trigger invalid fence handling and possible GPU or driver DoS without evidence of memory corruption or privilege escalation. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can likely be auto-closed for urgent security triage because the patch is a validation fix for an unsupported GPU feature and shows no concrete UAF, OOB write, arbitrary write, information leak, or privilege escalation path. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amdgpu/jpeg: set no_user_fence for JPEG v5.0.1 ring [ Upstream Commit: d0f6ae14c0452be4fc3aa5cf81c74e68b3243050 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d0f6ae14c0452be4fc3aa5cf81c74e68b3243050 Changed files: drivers/gpu/drm/amd/amdgpu/jpeg_v5_0_1.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=d0f6ae14c0452be4fc3aa5cf81c74e68b3243050 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63841 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63841 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:N/I:N/A:L 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).