From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68255][MODERATE 7.0] drm/virtio: bound EDID block reads to the response buffer Date: Mon, 10 Aug 2026 10:14:28 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68255 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: 3 X-AL-KERNEL-Commit: 9fc2a017c5d597937e0c28b9a9669844aa796c42 List-Id: CVE: CVE-2026-68255 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: drm/virtio: bound EDID block reads to the response buffer Commit: 9fc2a017c5d597937e0c28b9a9669844aa796c42 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9fc2a017c5d597937e0c28b9a9669844aa796c42 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68255 Analysis date: Mon, 10 Aug 2026 10:14:28 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A malicious virtio-gpu backend can advertise inconsistent EDID size and extension data so that virtio_get_edid_block reads beyond the fixed EDID response buffer and exposes adjacent guest kernel memory through parsed EDID data. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68255 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68255 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-2026-68255 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N';CWE-125;*CWE-200;*CWE-20;Other CVSS 'AV:A/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '6.5';DESCR 'An out of bounds read in the virtio-gpu EDID path can occur because virtio_get_edid_block validates the requested offset only against the device supplied resp size and not against the fixed resp edid array. A malicious virtio-gpu backend can advertise a large EDID size and extension count so that later EDID block reads copy data past the array into the parsed EDID buffer. This can disclose adjacent guest kernel memory through EDID data exposed by the DRM stack. For the CVSS the PR:N is used for the paranoid score because the attacker controls the virtual GPU backend relative to the guest and does not need credentials inside the guest OS. The issue is not Internet reachable as normal TCP IP traffic. It is reachable through the virtual device boundary and is most relevant to hostile host, compromised hypervisor, or untrusted device backend scenarios. Impact is information disclosure only based on the patch evidence, with no demonstrated write primitive or direct privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES OOB VIRT SIMPLEFIX LEAK HARDWARE LINUS INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Firmware-mediated external influence: +1 The attacker influence comes through a malicious or compromised virtio-gpu backend, not ordinary TCP/IP network traffic. * Confidentiality impact plausible: +1 The patch and commit explicitly describe an out-of-bounds read where adjacent guest kernel memory can be copied into the parsed EDID data. * Broad/default/common subsystem or broadly deployed exposure: +1 virtio-gpu is a common virtual GPU device in Linux guest deployments, especially desktop, cloud, CI, and virtualized workstation environments. Paranoid additional signal: * Security-boundary bypass with practical sensitive-object access: +2 In a threat model where the virtio backend is untrusted relative to the guest, this crosses the virtual device boundary and can expose guest kernel memory through EDID data. This is still an information disclosure primitive, not an arbitrary write or privilege escalation primitive. Signals not applied: * Remote reachable / network-triggerable: +0 This is not directly reachable over normal network traffic. * Generic memory corruption: +0 The primitive is an OOB read only. The patch does not show OOB write, UAF, double free, type confusion, arbitrary write, or refcount corruption. * Privilege escalation plausible: +0 No LPE path is demonstrated by the patch. The impact is information disclosure only. * Reliable kernel crash / strong DoS: +0 The described issue is disclosure through EDID parsing, not a reliable crash. ## 3. Reachability analysis The realistic attacker is a malicious virtio-gpu backend, compromised hypervisor component, hostile device model, or untrusted virtual device provider. A normal local user inside the guest generally cannot trigger the bug unless they can influence the virtio-gpu backend or the EDID response path. Namespaces and containers do not meaningfully reduce the privilege requirement inside the guest because the controlling input is supplied by the virtual device backend. From the guest CVSS perspective, PR:N can be defensible for the paranoid model because the attacker does not need guest credentials. From an infrastructure perspective, controlling the backend is usually privileged host-side access. The path is not Internet-exposed as TCP/IP traffic. It is exposed through the virtio device boundary and is relevant mainly for VM, cloud, sandbox, or confidential-computing-style threat models where device backends are not fully trusted. ## 4. Severity interpretation This behaves like an actionable Moderate information disclosure issue. It is not an ordinary low-risk bounds cleanup because the commit identifies a concrete OOB read and a user-visible disclosure channel via parsed EDID data. Theoretical impact is guest kernel memory disclosure. Realistic exploitation depends on whether the attacker can control the virtio-gpu backend or EDID response. There is no evidence of write corruption, privilege escalation, or reliable DoS, so it should not be treated as Important solely from the patch. However, because it crosses a virtualization device boundary and leaks kernel memory, it should not be auto-closed. ## 5. One-sentence report phrase A malicious virtio-gpu backend can advertise inconsistent EDID size and extension data so that virtio_get_edid_block reads beyond the fixed EDID response buffer and exposes adjacent guest kernel memory through parsed EDID data. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: concrete OOB read and kernel memory disclosure are present, and the risk depends heavily on the product threat model for virtio backends, confidential guests, and untrusted device emulation. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/virtio: bound EDID block reads to the response buffer Commit: 9fc2a017c5d597937e0c28b9a9669844aa796c42 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9fc2a017c5d597937e0c28b9a9669844aa796c42 Commit description: virtio_get_edid_block() validates the read offset only against the device-supplied resp->size field, never against the fixed-size resp->edid array. The EDID block index is driven by the device-supplied extension count, so a malicious virtio-gpu backend can advertise a large size together with a high block count and read far past the array into adjacent kernel memory, which is then surfaced in the parsed EDID (an out-of-bounds read / info leak). Also reject any read whose end exceeds the size of the edid array. Conforming EDID responses stay within the array and are unaffected. Fixes: b4b01b4 ("drm/virtio: add edid support") Cc: stable@vger.kernel.org Signed-off-by: Bryam Vargas Signed-off-by: Dmitry Osipenko Link: https://patch.msgid.link/20260620-b4-disp-22bba7bf-v1-1-b95924cee742@proton.me Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/virtio/virtgpu_vq.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=9fc2a017c5d597937e0c28b9a9669844aa796c42 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68255 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68255 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:A/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N The Best / paranoid CVSS score: 6.5 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: 3 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).