From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99118][LOW] drm/i915/dmc: Harden DMC firmware payload parsing [ Upstream Date: Fri, 30 Oct 2026 11:03:46 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99118 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: dfcfe2874e7c16e8460dc86ac1eeb54ea0e7f8aa List-Id: CVE: CVE-2026-99118 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: drm/i915/dmc: Harden DMC firmware payload parsing [ Upstream Commit: dfcfe2874e7c16e8460dc86ac1eeb54ea0e7f8aa Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dfcfe2874e7c16e8460dc86ac1eeb54ea0e7f8aa Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99118 Analysis date: Fri, 30 Oct 2026 11:03:46 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: Malformed administrator-supplied i915 DMC firmware can wrap its payload size, leaving a small allocation paired with a large logical size and potentially causing out-of-bounds reads and GPU availability failure. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99118 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99118 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-2026-99118 LOW https://www.kernelcve.org/list/?q=CVE-2026-99118 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE AEGIS_AS=0 LEGACY=LOW RESULT=DIFF (final Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H';CWE-190;*CWE-20;CWE-125;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:H';BEST CVSS score: '5.6';DESCR 'A malformed i915 DMC firmware header can overflow the conversion of fw_size from dwords to bytes, producing a small payload allocation while retaining a much larger dmc_fw_size value. Downstream DMC loading may then read beyond the allocated payload and perform an excessive or invalid sequence of device MMIO programming operations, creating a credible GPU hang or kernel availability impact. No UAF, kernel memory OOB write, arbitrary write, or proven attacker readable information leak is established. For the CVSS the PR:H value is selected because reliable exploitation normally requires administrative control over the requested i915 DMC firmware file or initramfs. The issue is not directly network reachable. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.6 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were KPANIC_UNSUPPORTED_REMOVED and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE SIMPLEFIX LEAK HARDWARE KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=YES NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=RECOMMENDED AutoDowngradeAllowed=YES RequiresHostUID0=UNKNOWN AuthorizationDecisionBypass=NO ProtectedResourceImpact=NONE B4PendingReview=NO B4PendingConfirmed=NO 1. ActionableScore * Raw base score: 1. * Conservative score: 1; no floor or cap applied. * Raw paranoid score: 1. * Paranoid score: 1; stronger corruption effects are unsupported. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 weak/indirect corruption candidate: unchecked dword-to-byte multiplication can wrap, allocate a small payload, and retain a much larger `dmc_fw_size` for later consumption. * +1 credible availability effect: supplied analysis supports excessive payload reads or invalid DMC/MMIO programming causing a GPU hang or kernel availability problem. * +1 broad exposure: DMC firmware loading is exercised on broadly deployed Intel graphics hardware. * -2 proven host-administrator-equivalent prerequisite: the supplied evidence says reliable triggering requires administrative control of the i915 firmware file or initramfs. Not awarded: * No heap or kernel-memory OOB write is shown; the immediate `memcpy()` is bounded by the wrapped allocation size. * No disclosure path, arbitrary write, UAF, controlled reclaim, protected-state change, or LPE is established. * No extra availability point: GPU hang and kernel availability are the same consequence. * B5-R does not apply: there is no retry-accumulated index and no confirmed OOB write. * B3-PENDING and checksum-metadata profiles do not apply. * No authorization guard changes DENY to ALLOW, so B4-PENDING is inapplicable. 3. Reachability analysis The malformed input is DMC firmware loaded by the i915 driver. Supplied evidence supports a host-administrator-controlled firmware/initramfs prerequisite, not render-node or ordinary DRM ioctl reachability. No namespace-scoped route, remote path, delegated display-service trigger, or unusual physical hardware requirement is shown. Exact numeric UID 0 is unresolved because equivalent administrative firmware control may be exercised through privileged provisioning mechanisms. 4. Primitive and severity reading The primitive is an integer-overflow-induced allocation/logical-size mismatch: a small heap payload is allocated and copied, while a large dword count may later drive reads and device programming. This supports invalid active state, a likely heap OOB read, and availability impact, but not a heap overwrite or useful corruption primitive. The downstream loader is not included, so the exact read bounds and MMIO behavior remain partly unverified. This is CLASS_C, not NEW52 B5-R. ImportantCandidate is NO and auto-downgrade is allowed because the full trigger is host-admin controlled and no separate security boundary is crossed. 5. One-sentence report phrase Malformed administrator-supplied i915 DMC firmware can wrap its payload size, leaving a small allocation paired with a large logical size and potentially causing out-of-bounds reads and GPU availability failure. 6. Manual review advice MANUAL CHECK RECOMMENDED Verify the downstream DMC transfer loop and whether any read data can escape device-local handling, but the supplied evidence does not establish an Important-grade write primitive. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/i915/dmc: Harden DMC firmware payload parsing [ Upstream Commit: dfcfe2874e7c16e8460dc86ac1eeb54ea0e7f8aa Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dfcfe2874e7c16e8460dc86ac1eeb54ea0e7f8aa Changed files: drivers/gpu/drm/i915/display/intel_dmc.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=dfcfe2874e7c16e8460dc86ac1eeb54ea0e7f8aa ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99118 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99118 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:H/UI:N/S:U/C:N/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.6 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: 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).