From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80700][MODERATE 7.0] drm/vmwgfx: validate external BO copy bounds for both stride paths Date: Fri, 28 Aug 2026 04:07:25 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80700 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 8 X-AL-KERNEL-ActionableScore-Lower: 7 X-AL-KERNEL-Commit: 4e0f669e2951b742239c6fe847fcc406fe78748d List-Id: CVE: CVE-2026-80700 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: drm/vmwgfx: validate external BO copy bounds for both stride paths Commit: 4e0f669e2951b742239c6fe847fcc406fe78748d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4e0f669e2951b742239c6fe847fcc406fe78748d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80700 Analysis date: Fri, 28 Aug 2026 04:07:25 -0400 ActionableScore: 8 ActionableScore lower bound: 7 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A bounds validation flaw in vmwgfx external BO copy allows a local DRM user to craft imported framebuffer state that can make memcpy read or write past the end of mapped buffer objects, causing kernel memory corruption and likely DoS with possible privilege escalation requiring manual review. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80700 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80700 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-2026-80700 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT 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:H/A:H';*CWE-787;CWE-125;CWE-190;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'A bounds validation flaw in vmwgfx external BO copy can allow an out-of-bounds read or write when copying imported dma-buf backed framebuffers. The vulnerable path trusts caller controlled offsets, strides, and height from plane state, and a crafted atomic commit on a configured CRTC can make memcpy operate past the end of the source or destination vmap. For the CVSS the PR:L is used because reliable triggering requires local access to the DRM/vmwgfx graphics interface or an equivalent local graphics session, but not full administrator privileges. The issue is not network reachable. Impact is at least local denial of service via kernel crash and in the worst case may allow confidentiality and integrity impact or privilege escalation because the bug includes an out-of-bounds write primitive in kernel mapped memory.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8) YES WRITE OOB HARDWARE LINUS KPANIC MEMORY DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=8 ActionableScoreLower=7 ## 1. ActionableScore * Conservative score: 7 * Paranoid score: 8 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum** ## 2. Signal breakdown * Local unprivileged trigger: +1. A local user with access to the DRM/vmwgfx interface and a configured CRTC can submit a crafted atomic commit using an imported framebuffer. * Memory corruption, strong corruption primitive: +2. The bug can drive memcpy past the end of source or destination vmaps, including an out-of-bounds write path. * Reliable kernel crash / strong DoS: +1. Out-of-bounds access from a kernel vmap copy path can realistically crash the kernel. * Confidentiality impact plausible: +1. The source-side out-of-bounds read may expose adjacent mapped memory depending on layout and copy direction. * Integrity impact plausible: +1. The destination-side out-of-bounds write can corrupt memory beyond the intended BO mapping. * Availability impact realistic: +1. Kernel crash is a realistic outcome, not just a warning. * Weak LPE concern in paranoid score: +1. The primitive is an OOB write in kernel mapped memory, but the exact target and exploitability are not demonstrated, so this is weaker than a proven LPE primitive. Not counted: * Remote reachable: +0. This is not network-triggerable. * Requires admin/root/CAP_SYS_ADMIN: +0. Typical DRM access can be granted to local graphical users and does not necessarily require full root. * Dirty-Pipe-like ownership/COW violation: +0. The patch shows imported dma-buf copy bounds issues, but not a supported file-backed COW or page-cache ownership bypass. * Race penalty: +0. This is not a timing race. ## 3. Reachability analysis The realistic trigger is local access to the VMware graphics DRM device, plus the ability to configure a CRTC and submit an atomic commit involving an imported dma-buf framebuffer. This usually maps to PR:L rather than PR:H, because graphical sessions commonly grant users access to DRM device nodes. Containers reduce exposure unless the DRM device is passed through. The affected path is not a generic Linux default path, but it is relevant in VMware guest environments using vmwgfx and dma-buf framebuffer import. ## 4. Severity interpretation This is stronger than an ordinary Moderate issue because the patch fixes explicit bounds failures in both bulk and row-by-row copy paths, including unsigned subtraction wrap, multiplication overflow, and missing endpoint validation. The realistic demonstrated impact is local kernel crash or memory corruption. Theoretical privilege escalation is plausible enough for manual review because the bug includes a destination OOB write in kernel mapped memory, but the patch does not prove controlled target selection or a full exploit chain. ## 5. One-sentence report phrase A bounds validation flaw in vmwgfx external BO copy allows a local DRM user to craft imported framebuffer state that can make memcpy read or write past the end of mapped buffer objects, causing kernel memory corruption and likely DoS with possible privilege escalation requiring manual review. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch shows a concrete OOB read/write primitive in a kernel graphics driver copy path reachable from local DRM operations. This should not be auto-closed even if practical exploitation beyond DoS is not yet demonstrated. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/vmwgfx: validate external BO copy bounds for both stride paths Commit: 4e0f669e2951b742239c6fe847fcc406fe78748d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4e0f669e2951b742239c6fe847fcc406fe78748d Commit description: vmw_external_bo_copy() trusts caller-supplied offsets, strides, and heights and operates on imported dma-buf vmaps: - The equal-stride memcpy() bound was clamped after subtracting the offsets from dst_size and src_size; an offset larger than the BO size wraps the unsigned subtraction to a huge value and the resulting memcpy() runs off the end of the vmap. dst_stride * height is also a u32 multiplication that can overflow. - The non-equal-stride row-by-row path had no bound at all. The loop touches bytes through offset + (height - 1) * stride + width_in_bytes, with only a WARN_ON(dst_stride < width_in_bytes), and could likewise step past the end of either mapping. The offsets and strides are derived from STDU/SOU plane state, so a configured CRTC submitting a crafted atomic commit on an imported framebuffer can reach this path. Validate the exact row-copy endpoint against each BO's size up front using check_mul_overflow() and check_add_overflow(). Use the bulk memcpy() path only when width_in_bytes covers the whole stride; otherwise copy one row at a time so partial-row updates near the bottom of a framebuffer remain valid. Also reject zero strides and stride < width_in_bytes, both of which the row-by-row path cannot represent safely. Fixes: 50f1199 ("drm/vmwgfx: Fix prime with external buffers") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4.7 Signed-off-by: Zack Rusin Reviewed-by: Ian Forbes Link: https://patch.msgid.link/20260505222728.519626-13-zack.rusin@broadcom.com Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/vmwgfx/vmwgfx_blit.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=4e0f669e2951b742239c6fe847fcc406fe78748d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80700 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80700 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:L/A:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7.8 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: 7 Paranoid ActionableScore: 8 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: YES 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).