From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72313][LOW] drm/fb-helper: Only consider active CRTCs for vblank sync [ Upstream Date: Sun, 16 Aug 2026 05:46:16 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72313 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 7d84acf641afb68aa8efe40815ef43779ddb12fd List-Id: CVE: CVE-2026-72313 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: drm/fb-helper: Only consider active CRTCs for vblank sync [ Upstream Commit: 7d84acf641afb68aa8efe40815ef43779ddb12fd Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7d84acf641afb68aa8efe40815ef43779ddb12fd Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72313 Analysis date: Sun, 16 Aug 2026 05:46:16 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: The DRM fb-helper dirty update path could wait for vblank on the wrong or inactive CRTC, causing vblank timeout warnings and limited local denial of service through delayed display updates. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72313 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72313 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: LOW 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-2026-72313 LOW 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-754;CWE-703;**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 fbdev dirty update path in drm fb helper could wait for vblank on CRTC 0 even when the fbdev output was displayed on another active CRTC or not displayed on an active CRTC at all. This can produce repeated vblank wait timeouts and kernel warnings in drm_crtc_wait_one_vblank, which may delay display updates and degrade local system responsiveness. For the CVSS the PR:L is used because a local user or process normally needs access to fbdev or another local path that causes fbdev dirty updates. The issue is not network reachable and is not triggered by packet traffic. Impact is denial of service only through timeout based stalls or warning spam, with no evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) SKIP CVE-2026-72313 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: d8c4bddcd8bcb41885d3db2ba18c840c411564c2 YES NO NO unknown MAYBE LOCK DEADLOCK INIT WARNONLY HARDWARE LINUS INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 ## 1. ActionableScore * Conservative score: 1 * Paranoid score: 1 * Final recommended bucket: **Ordinary Moderate / Low-like** ## 2. Signal breakdown Triggered signals: * Local user or local process trigger: +1 The issue is reachable through local fbdev dirty update activity on systems using DRM fb-helper. Not triggered: * Remote reachable: +0 No network or packet-processing path is involved. * Generic memory corruption: +0 The patch does not show UAF, OOB access, double-free, type confusion, refcount misuse, arbitrary write, or stale pointer reuse. * Reliable kernel crash / strong DoS: +0 The observed failure is a vblank wait timeout and WARN, not a demonstrated panic, BUG, oops, or persistent system-wide crash. * Availability impact realistic: +0 There can be display update delay or warning spam, but the impact is limited and not shown to be persistent or system-wide beyond the timeout path. * Requires admin/root/CAP_*: +0 Direct modeset configuration may require privileges, but dirty updates may be caused by local graphical or fbdev users. No full admin requirement is necessary for the conservative local-trigger interpretation. * Rare/difficult-to-reach subsystem: +0 DRM fbdev emulation is configuration-dependent, but it is a normal local display path and should not be heavily penalized. ## 3. Reachability analysis A local user or process that can cause fbdev dirty updates may trigger the affected path. Practical reachability depends on device permissions, fbdev exposure, DRM driver behavior, and whether fbdev emulation is used. Containers usually do not expose DRM or fbdev devices unless explicitly delegated, so container reachability is deployment-specific. The issue is not remotely reachable and is not triggered by network traffic. ## 4. Severity interpretation This behaves like a Low-like or ordinary Moderate availability issue rather than an Important kernel vulnerability. The patch fixes incorrect CRTC selection for vblank synchronization. The realistic effect is warning output and timeout-based delay when fbdev output is not on CRTC 0. There is no supported memory corruption primitive, no privilege escalation path, and no confidentiality or integrity impact. ## 5. One-sentence report phrase The DRM fb-helper dirty update path could wait for vblank on the wrong or inactive CRTC, causing vblank timeout warnings and limited local denial of service through delayed display updates. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be auto-closed for security triage unless the affected product has evidence that vblank timeout warnings are configured to panic the kernel or that untrusted users can repeatedly trigger a broader system-wide failure. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/fb-helper: Only consider active CRTCs for vblank sync [ Upstream Commit: 7d84acf641afb68aa8efe40815ef43779ddb12fd Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7d84acf641afb68aa8efe40815ef43779ddb12fd Changed files: drivers/gpu/drm/drm_vblank.c drivers/gpu/drm/drm_fb_helper.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=7d84acf641afb68aa8efe40815ef43779ddb12fd ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72313 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72313 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: unknown Paranoid ActionableScore: 1 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).