From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-97575][MODERATE 7.0] media: v4l2-ctrls: validate AV1 tile counts Date: Tue, 29 Sep 2026 01:13:55 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-97575 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: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 85df9fc79b07f1cc7c953f930ae7e675d0c1e820 List-Id: CVE: CVE-2026-97575 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: media: v4l2-ctrls: validate AV1 tile counts Commit: 85df9fc79b07f1cc7c953f930ae7e675d0c1e820 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=85df9fc79b07f1cc7c953f930ae7e675d0c1e820 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97575 Analysis date: Tue, 29 Sep 2026 01:13:55 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: Malformed AV1 tile counts supplied through a stateless V4L2 decoder control can drive out-of-bounds array and descriptor processing, causing at least a local kernel crash and potentially driver-dependent kernel memory corruption. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97575 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97575 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-2026-97575 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-97575 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:H/A:H';*CWE-20;CWE-129;CWE-125;*CWE-787;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'The V4L2 AV1 frame control accepts tile_cols and tile_rows values without enforcing the architectural maximums used by stateless AV1 decoder drivers. These fields are used as loop bounds and array indices and their product controls the number of per tile descriptors, so oversized values can cause out of bounds reads and may cause writes beyond driver allocated descriptor buffers. For the CVSS the PR:L value is used because an attacker must execute a local process with access to a stateless V4L2 decoder device and submit crafted controls through ioctl. The issue is not directly network reachable, although a local media service processing an untrusted remote AV1 stream could provide an indirect path if it forwards attacker controlled tile metadata. Impact is at least denial of service through a kernel crash and may include confidentiality or integrity impact through kernel memory corruption. The paranoid score uses C:H/I:H/A:H because a plausible out of bounds write in per tile descriptor generation can support privilege escalation, but the exact primitive depends on the consuming decoder driver and requires manual confirmation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE HARDWARE LINUS KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 PrimitiveClass=CLASS_B RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO ## 1. ActionableScore * Raw conservative score: 4 * Conservative score: 4 * Raw paranoid score: 5 * Paranoid score: 5 * No floor or cap was applied. * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: ## 2. Signal breakdown Conservative signals: * +1 Weak or indirect corruption candidate. Attacker-controlled tile counts are used as loop bounds and indices into fixed-size arrays, establishing unsafe out-of-range structured access. * +1 Reliable kernel crash or strong DoS. Values up to 255 can drive decoder processing beyond architectural tile limits, making an invalid kernel access and crash realistic. * +1 Local unprivileged trigger. A process with access to the stateless decoder device can submit the malformed AV1 frame control through ordinary V4L2 ioctls without an administrative capability. * +1 Local unprivileged high-control kernel data-plane API. The process directly controls the counts used for array indexing, loop iteration, division, and descriptor-count calculation. Paranoid difference: * +2 replaces the conservative +1 corruption candidate. Per-tile descriptor generation plausibly performs writes beyond a fixed descriptor allocation when the attacker-controlled product exceeds `V4L2_AV1_MAX_TILE_COUNT`. This is technically defensible but requires consumer-driver confirmation. Not awarded: * No UAF or stale-lifetime primitive is established. * Controlled target selection, arbitrary write, controlled reclaim, and callback influence are not demonstrated. * Confidentiality is not separately awarded because no read-back or disclosure path is shown. * Integrity is not separately awarded because the exact overwritten object and write contents are not visible. * Remote reachability is not established. A network media service would only provide an indirect deployment-specific path. * No additional Availability point is awarded because it would duplicate the same prospective kernel crash. * No hardware rarity penalty is applied. A compatible stateless AV1 decoder is required, but the supplied evidence does not establish genuinely rare hardware. ## 3. Reachability analysis The direct attacker is a local process that can open a stateless V4L2 AV1 decoder device and submit `V4L2_CTRL_TYPE_AV1_FRAME`. The control operation itself does not normally require host root or an administrative capability, so below-host-admin reachability exists where device-node permissions grant access. This is not a namespace-capability path, and user or network namespaces do not independently provide access to the decoder. Device provisioning and permissions are prior host-controlled setup, but triggering after access has been granted does not require host administration. A compatible decoder and driver are required. The attacker controls the malformed tile dimensions but does not need a race or special timing. Direct network triggering is unsupported. A remote stream may become an indirect input only when a local media service converts its metadata into stateless V4L2 controls without validation. ## 4. Primitive and severity interpretation The exact established primitive is unchecked attacker-controlled indexing and loop bounding in stateless AV1 decoder consumers. Oversized `tile_cols` or `tile_rows` can exceed the fixed `mi_*_starts[]` and `*_in_sbs_minus_1[]` limits. Their product can also exceed the maximum per-tile descriptor count. The visible patch establishes a concrete OOB-access condition, but it does not show all consuming drivers or prove the direction and contents of every access. Therefore, this is CLASS_B rather than CLASS_A. The conservative interpretation is an invalid structured access capable of crashing the kernel. The paranoid interpretation is an attacker-influenced sequential OOB write during per-tile descriptor construction. This is not cleanup-only behavior and does not involve a repeated release or refcount mutation. ImportantCandidate is YES because a driver-specific OOB write remains plausible and would materially change the issue from crash-only to exploitable kernel corruption. AutoDowngradeAllowed is NO because automatically closing the issue as ordinary DoS could discard that unresolved corruption primitive. Likely operational severity is Actionable Moderate until affected decoder call sites confirm whether descriptor generation can write beyond its allocation. Confirmation of an attacker-influenced OOB write could support Important-class treatment. ## 5. One-sentence report phrase Malformed AV1 tile counts supplied through a stateless V4L2 decoder control can drive out-of-bounds array and descriptor processing, causing at least a local kernel crash and potentially driver-dependent kernel memory corruption. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Review every stateless AV1 driver consuming `tile_cols`, `tile_rows`, and their product to determine whether the out-of-range loops perform reads only or write per-tile descriptors beyond fixed allocations. ## 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: media: v4l2-ctrls: validate AV1 tile counts Commit: 85df9fc79b07f1cc7c953f930ae7e675d0c1e820 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=85df9fc79b07f1cc7c953f930ae7e675d0c1e820 Commit description: The stateless AV1 decoders use tile_info.tile_cols and tile_rows as loop bounds and as indices into the mi_*_starts[] and *_in_sbs_minus_1[] arrays, as the divisor for context_update_tile_id, and their product bounds the per-tile descriptor buffers, but std_validate_compound() does not bound these u8 fields. Reject a V4L2_CTRL_TYPE_AV1_FRAME whose tile_cols or tile_rows exceeds V4L2_AV1_MAX_TILE_COLS / _ROWS, or whose product exceeds V4L2_AV1_MAX_TILE_COUNT. A zero tile count is left to the consuming driver so the zero-initialised control that existing userspace submits is still accepted. Fixes: 9de30f5 ("media: Add AV1 uAPI") Assisted-by: Claude:claude-opus-4-8 Cc: stable@vger.kernel.org Signed-off-by: Michael Bommarito Reviewed-by: Benjamin Gaignard Signed-off-by: Hans Verkuil Signed-off-by: Greg Kroah-Hartman Changed files: drivers/media/v4l2-core/v4l2-ctrls-core.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=85df9fc79b07f1cc7c953f930ae7e675d0c1e820 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97575 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97575 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: 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: 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).