From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74444][MODERATE 7.0] drm/vmwgfx: validate DRAW_PRIMITIVES header size before division Date: Sat, 15 Aug 2026 15:59:11 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74444 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: 4 X-AL-KERNEL-Commit: 2666cddf0dd218aa9bd1f99db688d1b532eac21a List-Id: CVE: CVE-2026-74444 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/vmwgfx: validate DRAW_PRIMITIVES header size before division Commit: 2666cddf0dd218aa9bd1f99db688d1b532eac21a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2666cddf0dd218aa9bd1f99db688d1b532eac21a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74444 Analysis date: Sat, 15 Aug 2026 15:59:11 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A user-controlled vmwgfx DRAW_PRIMITIVES command can use an undersized header to trigger unsigned arithmetic underflow, bypass bounds validation, and cause an out-of-bounds kernel memory read that may crash the kernel and may have limited confidentiality impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74444 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74444 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-2026-74444 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:H/I:N/A:H';CWE-191;CWE-125;*CWE-20;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '7.1';DESCR 'A user controlled DRAW_PRIMITIVES command in vmwgfx can set header size smaller than the command body size, causing an unsigned subtraction underflow before maxnum is calculated. This makes the bounds check accept a large numVertexDecls value and lets the validation loop read decl entries far beyond the kernel command bounce buffer. For the CVSS the PR:L is used because a local process with access to the vmwgfx DRM device can submit the command stream without requiring full administrative privileges. The issue is not network reachable and requires local access to the graphics device interface. Impact is at least local denial of service via kernel crash and may include confidentiality impact because the primitive is an out-of-bounds kernel memory read, but integrity impact is not supported by the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES OOB SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. A local process with access to the vmwgfx DRM device can submit a user-controlled command stream. * Reliable kernel crash / strong DoS: +1. The underflow can make validation read far beyond the command bounce buffer, plausibly causing an Oops or kernel crash. * Confidentiality impact plausible: +1. The primitive is an out-of-bounds kernel memory read, although the patch does not show a direct reliable disclosure channel. * Availability impact realistic: +1. The trigger is simple once the device interface is reachable and can affect the host kernel or guest kernel availability. Paranoid additional signal: * Weak/indirect memory-safety concern: +1. This is not an OOB write or UAF, but it is a concrete kernel OOB read caused by attacker-controlled size arithmetic and attacker-controlled loop bounds. Not awarded: * No remote/network trigger. * No strong memory corruption primitive. * No integrity impact. * No Dirty-Pipe-like ownership or page-cache corruption. * No strong LPE plausibility. Call-site confidence: high. The vulnerable calculation and the fixed validation are in the provided vmw_cmd_draw() context, and the commit message explicitly describes the OOB read path. ## 3. Reachability analysis The bug is reachable by a local user process that can access the vmwgfx DRM device and submit a crafted DRAW_PRIMITIVES command. This normally means access to VMware graphics DRM nodes, commonly via local desktop, render, or video group style permissions depending on distribution policy. The issue is not network reachable. Containers only matter if the vmwgfx DRM device is passed into the container or the container has equivalent device access. The path is deployment-dependent because vmwgfx is primarily relevant to VMware virtual GPU environments, but within those environments the interface can be a normal local user-facing graphics path. ## 4. Severity interpretation This behaves like an actionable Moderate issue rather than an ordinary low-risk validation fix. The patch fixes a concrete unsigned underflow that leads to a kernel out-of-bounds read, not just a warning or harmless reject path. Realistic impact is local denial of service via kernel crash. Confidentiality impact is plausible because kernel memory is read out of bounds, but the patch does not demonstrate a reliable leak back to userspace. Privilege escalation is not strongly supported because there is no write primitive, UAF reclaim, callback control, refcount takeover, or object replacement shown. ## 5. One-sentence report phrase A user-controlled vmwgfx DRAW_PRIMITIVES command can use an undersized header to trigger unsigned arithmetic underflow, bypass bounds validation, and cause an out-of-bounds kernel memory read that may crash the kernel and may have limited confidentiality impact. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a concrete local kernel memory-safety issue with attacker-controlled input and an OOB read primitive. It is not strong enough for automatic Important classification, but it should not be auto-closed as an ordinary Moderate without checking device exposure and whether the OOB read can influence disclosure or stability. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/vmwgfx: validate DRAW_PRIMITIVES header size before division Commit: 2666cddf0dd218aa9bd1f99db688d1b532eac21a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2666cddf0dd218aa9bd1f99db688d1b532eac21a Commit description: vmw_cmd_draw() computes maxnum = (header->size - sizeof(cmd->body)) / sizeof(*decl); where header->size is u32 and is taken straight from the user-supplied command stream. When header->size is less than sizeof(cmd->body) the unsigned subtraction wraps to nearly 4 GiB, producing a huge maxnum. Any user-controlled cmd->body.numVertexDecls then passes the bound and the loop dereferences decl[i] far past the end of the kernel command bounce buffer, producing an out-of-bounds read of kernel memory. Reject undersized headers up front. Fixes: 7a73ba7 ("drm/vmwgfx: Use TTM handles instead of SIDs as user-space surface handles.") 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/20260505222728.519626-7-zack.rusin@broadcom.com Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.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=2666cddf0dd218aa9bd1f99db688d1b532eac21a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74444 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74444 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:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H The Best / paranoid CVSS score: 7.1 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: 4 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).