From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-99097][MODERATE REGULAR] tee: shm: reject zero-sized allocations in tee_dyn_shm_alloc_helper() Date: Mon, 26 Oct 2026 22:55:14 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-99097 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 1 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: e5dc7af9c3a5373ee7a84959126e7dfa9e4ad50d List-Id: CVE: CVE-2026-99097 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: tee: shm: reject zero-sized allocations in tee_dyn_shm_alloc_helper() Commit: e5dc7af9c3a5373ee7a84959126e7dfa9e4ad50d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5dc7af9c3a5373ee7a84959126e7dfa9e4ad50d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99097 Analysis date: Mon, 26 Oct 2026 22:55:14 -0400 ActionableScore: 1 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: A permitted local TEE client can submit a zero-sized shared-memory allocation that triggers an allocator warning and conditionally panics `panic_on_warn` kernels, without shown memory corruption. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99097 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99097 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 REGULAR 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-2026-99097 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99097 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE RESULT=DIFF TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC) 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-20;CWE-754;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A local process can submit TEE_IOC_SHM_ALLOC with size equal to zero, causing tee_dyn_shm_alloc_helper to pass a zero size allocation to alloc_pages_exact. This reaches get_order(0), produces an excessive allocation order, and triggers a page allocator warning before the allocation fails. For the CVSS the PR:L value is used because a local process and access to the TEE device interface are required. Normal configurations expose only a failed allocation and kernel warning, while panic_on_warn configurations can turn the warning into a system wide kernel panic. The demonstrated primitive is input validation failure and denial of service only, with no evidence of memory corruption, information disclosure, or privilege escalation. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to MODERATE because 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 INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and V30_AEGIS_DISTANCE_REVIEW_MODERATE and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 5.5 and ActionableScore 2 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE WARNONLY SIMPLEFIX INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 V30_AEGIS_DISTANCE_REVIEW_MODERATE V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=1 PrimitiveClass=CLASS_C RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES RequiresHostUID0=NO 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; conditional panic does not establish another distinct availability effect. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown * +1 Reliable kernel crash/strong DoS: a zero-size ioctl deterministically reaches an excessive allocation order; kernels configured with `panic_on_warn` can panic. * +0 Normal configuration: allocation fails after a warning, without memory corruption or persistent damage. * No local-unprivileged bonus: local TEE-device access is grounded, but unrestricted ordinary-user access is not shown; the supplied PR:L assessment supports below-host-admin access only. * No configuration penalty: `panic_on_warn` is conditional, but the evidence does not establish a rare-and-difficult configuration. * No B5-R signal: there is no heap OOB write, retry-accumulated index, or later consumption of corrupted structured state. * No UAF, overwrite, disclosure, authorization bypass, integrity impact, or privilege escalation is shown. * The same panic is not counted again as a separate availability point. 3. Reachability analysis A local process with permission to issue `TEE_IOC_SHM_ALLOC` can supply `size == 0`. The supplied assessment characterizes this as PR:L, supporting below-host-administrator reachability and no host UID 0 requirement. Device-node permission policy still controls exposure. No namespace capability, prior host configuration, race, retry sequence, or attacker-controlled memory-layout operation is involved. 4. Primitive and severity reading The exact defect is unchecked zero-sized allocation input causing `get_order(0)` to produce an excessive order, followed by an allocator warning and failed allocation. This is CLASS_C invalid-state/DoS behavior, not an OOB access or lifetime violation. A host panic is shown only when warnings are configured as fatal; normal behavior is warning plus allocation failure. There is no leverage past that failure, so this is not an Important candidate and automatic Moderate handling is permissible. 5. One-sentence report phrase A permitted local TEE client can submit a zero-sized shared-memory allocation that triggers an allocator warning and conditionally panics `panic_on_warn` kernels, without shown memory corruption. 6. Manual review advice NO MANUAL CHECK NEEDED The patch and call path establish only a narrowly conditional warning-to-panic denial of service. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: tee: shm: reject zero-sized allocations in tee_dyn_shm_alloc_helper() Commit: e5dc7af9c3a5373ee7a84959126e7dfa9e4ad50d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5dc7af9c3a5373ee7a84959126e7dfa9e4ad50d Commit description: tee_dyn_shm_alloc_helper() derives nr_pages from a caller-supplied size and passes it to alloc_pages_exact() without checking it. For size == 0 nr_pages is 0, and alloc_pages_exact(0) calls get_order(0), which is documented as undefined and returns BITS_PER_LONG - PAGE_SHIFT. The page allocator then trips its order > MAX_PAGE_ORDER warning and fails the allocation; on a panic_on_warn kernel that ends the boot. This can be triggered by TEE_IOC_SHM_ALLOC with struct tee_ioctl_shm_alloc_data where size is 0. Reject a zero page count, as register_shm_helper() already does for the register path. Fixes: cf44415 ("tee: optee: Move pool_op helper functions") Cc: stable@vger.kernel.org Cc: lvc-project@linuxtesting.org Signed-off-by: Georgiy Osokin Reviewed-by: Sumit Garg Signed-off-by: Jens Wiklander Signed-off-by: Greg Kroah-Hartman Changed files: drivers/tee/tee_shm.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=e5dc7af9c3a5373ee7a84959126e7dfa9e4ad50d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-99097 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99097 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: MODERATE KPANIC detected for this report: NO Published priority for this report (same as in Subject): MODERATE REGULAR 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).