From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68206][MODERATE 7.0] media: v4l2-ctrls: validate HEVC active reference counts Date: Mon, 10 Aug 2026 16:50:09 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68206 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: 9a998cc1c348769262d433acb7d238c5fac4b2e0 List-Id: CVE: CVE-2026-68206 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: media: v4l2-ctrls: validate HEVC active reference counts Commit: 9a998cc1c348769262d433acb7d238c5fac4b2e0 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9a998cc1c348769262d433acb7d238c5fac4b2e0 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68206 Analysis date: Mon, 10 Aug 2026 16:50:09 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A malformed HEVC stateless V4L2 slice control can provide active reference counts beyond the maximum DPB size, allowing a local process with decoder device access to trigger driver-specific invalid reference-list handling and likely DoS, with limited OOB impact possible in affected drivers. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68206 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68206 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-2026-68206 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:L/I:L/A:H';*CWE-20;CWE-125;*CWE-787;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.6';DESCR 'A malformed HEVC stateless V4L2 slice control can provide active L0 or L1 reference counts that exceed the maximum DPB entry count. The common validation path did not reject these counts before driver specific decode code consumed the control, so a local userspace process with access to the V4L2 decoder device could make a driver process an invalid reference list size. For the CVSS the PR:L is used because the attacker needs local access to a V4L2 device node or to a media service that queues these controls, but full administrator privileges are not normally required in systems where video devices are delegated to users or sandboxed media processes. The issue is not directly network reachable. Impact is at least local denial of service through a driver crash or hardware decode failure, and in the paranoid score it may allow limited confidentiality or integrity impact if a specific driver turns the invalid count into an out of bounds access.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES OOB SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 YES 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: * Local unprivileged trigger: +1. A local process with access to the V4L2 stateless HEVC decoder device can queue malformed HEVC slice controls. * Memory corruption, weak/indirect corruption candidate: +1. The unchecked active L0/L1 reference counts can be consumed by driver-specific code as array bounds or loop limits, but the patch does not show a concrete write primitive. * Availability impact realistic: +1. A malformed reference count can plausibly crash or wedge a media decoder driver or hardware decode path. Paranoid additional signals: * Confidentiality impact plausible: +1. If a specific driver uses the invalid count for reads from reference-list or DPB-related arrays, limited OOB read behavior is plausible. * Integrity impact plausible: +1. If a specific driver uses the invalid count while constructing hardware command buffers or per-frame metadata, limited OOB write or metadata corruption is possible. Capping and constraints: * This is primarily an input-validation fix, so conservative scoring is capped below Important without a concrete downstream primitive. * No strong memory-corruption primitive is demonstrated in the patch. * No arbitrary write, UAF, double-free, type confusion, callback control, or attacker-controlled reclaim is shown. * Call-site confidence: medium. The common validation path is visible, but the driver-specific consumers are not included in the provided patch. ## 3. Reachability analysis The bug is locally reachable through V4L2 stateless HEVC decoder controls, typically via `/dev/video*` device nodes. Full root privileges are not necessarily required because video devices are commonly delegated to users, media services, sandboxed browser or codec processes, or members of a `video`-like group. The issue is not directly network reachable. A remote file or stream could only become relevant if it is decoded by a local process that forwards attacker-controlled HEVC parameters into the V4L2 stateless decoder API. The affected path is configuration and hardware dependent. It requires a stateless HEVC V4L2 decoder driver and userspace using these controls. This is not a universal kernel path, but it is reachable through ordinary local media interfaces on systems with supported hardware. ## 4. Severity interpretation This behaves like an actionable Moderate issue rather than an ordinary low-risk validation bug. The realistic impact is local DoS through driver crash, decode failure, or hardware pipeline failure. The theoretical risk is higher because the invalid count is consumed by driver-specific code and may affect array indexing or metadata construction. However, without a shown OOB write, UAF, or controllable corruption sink, it should not be treated as a Strong Important candidate solely from this patch. The paranoid score is justified for manual-review sensitivity because a shared validation gap affects multiple stateless HEVC drivers, and some driver implementations may turn the invalid reference count into limited OOB read or write behavior. ## 5. One-sentence report phrase A malformed HEVC stateless V4L2 slice control can provide active reference counts beyond the maximum DPB size, allowing a local process with decoder device access to trigger driver-specific invalid reference-list handling and likely DoS, with limited OOB impact possible in affected drivers. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Manual review is required because the patch fixes common validation before driver-specific consumption, and the real impact depends on how individual stateless HEVC drivers use `num_ref_idx_l0_active_minus1` and `num_ref_idx_l1_active_minus1`. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: media: v4l2-ctrls: validate HEVC active reference counts Commit: 9a998cc1c348769262d433acb7d238c5fac4b2e0 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9a998cc1c348769262d433acb7d238c5fac4b2e0 Commit description: HEVC slice parameters are shared stateless V4L2 controls, but the common validation path does not verify the active L0/L1 reference counts before driver-specific code consumes them. The original report came from Cedrus, but the active count bounds are not Cedrus-specific. Validate them in the common HEVC slice control path so stateless HEVC drivers get the same basic guarantees as soon as the control is queued. Do not reject ref_idx_l0/ref_idx_l1 entries here. Existing userspace may use out-of-range sentinel values such as 0xff for missing references, and some hardware can use that information for concealment. Keep this common check limited to the active reference counts. Fixes: d395a78 ("media: hevc: Add decode params control") Cc: stable@vger.kernel.org Signed-off-by: Pengpeng Hou Reviewed-by: Nicolas Dufresne Signed-off-by: Nicolas Dufresne 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=9a998cc1c348769262d433acb7d238c5fac4b2e0 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68206 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68206 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:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 6.6 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).