From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53354][MODERATE 7.0] arm64: errata: Mitigate TLBI errata on various Arm CPUs Date: Wed, 01 Jul 2026 10:20:23 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53354 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: 7 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 925058203229403008d77a52b1e63e2ae5f4a3cf List-Id: CVE: CVE-2026-53354 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: arm64: errata: Mitigate TLBI errata on various Arm CPUs Commit: 925058203229403008d77a52b1e63e2ae5f4a3cf Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=925058203229403008d77a52b1e63e2ae5f4a3cf Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53354 Analysis date: Wed, 01 Jul 2026 10:20:23 -0400 ActionableScore: 7 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: CVE-2025-10263 is an Arm CPU TLBI completion erratum where writes translated by invalidated TLB entries may not be globally observed after TLBI/DSB, creating a local timing-dependent stale memory ordering risk with possible DoS and paranoid UAF-like integrity impact on affected arm64 systems. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53354 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53354 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-2026-53354 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-416;CWE-693;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'CVE-2025-10263 affects several Arm Cortex, Neoverse, and C1 CPUs where a broadcast TLBI/DSB sequence may complete before affected memory writes are globally observed. This can break the kernel assumption that writes translated by an invalidated TLB entry are complete after the barrier, creating a stale translation memory ordering risk around unmap, page table changes, and page reuse. For the CVSS the PR:L is chosen because practical triggering requires local code execution on an affected arm64 system, for example through memory management activity such as mmap, munmap, mprotect, fork, or exit. The issue is not directly network reachable. Impact is at least local denial of service or memory consistency failure, and in the paranoid case may allow confidentiality or integrity impact due to UAF-like stale write behavior after invalidated translations. AC:H is used because reliable exploitation depends on hardware timing, affected CPU models, and a narrow TLBI related race window.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6) YES HARDWARE KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=7 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 7 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1 Local user activity can plausibly exercise TLBI paths through memory-management operations such as mmap, munmap, mprotect, fork, exit, and page-table teardown. * Memory corruption, weak/indirect corruption candidate: +1 The bug is a hardware memory-ordering erratum, not a direct C-code UAF, but stale write completion after invalidated translations can plausibly corrupt memory after page-table changes or page reuse. * Real lifetime or ownership corruption concern: +1 The relevant risk is that writes translated by an invalidated TLB entry may complete after the kernel believes the mapping is gone, creating a stale-ownership style hazard. * Broad/default/common subsystem exposure: +1 TLBI and page-table invalidation are core arm64 MM operations, and the affected CPU list includes many Cortex, Neoverse, and C1 cores. * Hard or timing-dependent condition: -1 Reliable exploitation depends on affected hardware behavior, TLBI timing, memory ordering, and page reuse windows. * Availability impact realistic: +1 Memory consistency failures in core MM paths can realistically lead to crashes or system instability, though a concrete crash primitive is not shown in the patch. Conservative total: 4 Paranoid additional signals: * Weak LPE concern: +1 A stale write after unmap or page reuse may theoretically affect memory now owned by another object or privilege domain, but no controlled reclaim or write primitive is demonstrated. * Confidentiality impact plausible: +1 If stale memory effects cross ownership boundaries, limited disclosure or observation of inconsistent state is plausible, but not directly proven. * Integrity impact plausible: +1 The strongest concern is integrity impact from delayed writes landing after page ownership or mapping state has changed. Paranoid total: 7 ## 3. Reachability analysis The issue is not network reachable by itself. Triggering requires execution on an affected arm64 CPU and activity that drives kernel TLB invalidation paths. A local unprivileged process can plausibly create such activity through normal memory-management syscalls, but reliable exploitation would require difficult timing and affected hardware. Namespaces and containers do not remove the concern because container workloads still exercise host kernel MM and TLBI paths. However, the bug is hardware-dependent and only applies to listed Arm CPU families when the mitigation is absent. The affected path is core architecture MM behavior, not a niche driver path. The workaround is enabled through ARM64_WORKAROUND_REPEAT_TLBI for affected MIDR ranges. ## 4. Severity interpretation This is not an ordinary Moderate cleanup issue. It is a hardware erratum affecting core memory-management ordering. The patch does not show a direct arbitrary write, attacker-controlled reclaim, function-pointer overwrite, or demonstrated LPE chain, so the conservative score should not assume full exploitation. The theoretical risk is higher than a simple DoS because stale writes after invalidated translations can resemble UAF-like page ownership corruption around unmap and page reuse. Realistic exploitation evidence is limited and timing-dependent, but the primitive class is serious enough to avoid auto-closing. This should be treated as Actionable Moderate at minimum, with Strong Important candidate handling for affected arm64 platforms. ## 5. One-sentence report phrase CVE-2025-10263 is an Arm CPU TLBI completion erratum where writes translated by invalidated TLB entries may not be globally observed after TLBI/DSB, creating a local timing-dependent stale memory ordering risk with possible DoS and paranoid UAF-like integrity impact on affected arm64 systems. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a core arm64 MM hardware erratum with possible stale write and page ownership implications. The patch does not prove a practical LPE primitive, but the affected path is fundamental enough that affected products should receive manual platform and exposure review. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: arm64: errata: Mitigate TLBI errata on various Arm CPUs Commit: 925058203229403008d77a52b1e63e2ae5f4a3cf Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=925058203229403008d77a52b1e63e2ae5f4a3cf Commit description: A number of CPUs developed by Arm suffer from errata whereby a broadcast TLBI;DSB sequence may complete before the global observation of writes which are translated by an affected TLB entry. These errata ONLY affect the completion of memory accesses which have been translated by an invalidated TLB entry, and these errata DO NOT affect the actual invalidation of TLB entries. TLB entries are removed correctly. This issue has been assigned CVE ID CVE-2025-10263 . To mitigate this issue, Arm recommends that software follows any affected TLBI;DSB sequence with an additional TLBI;DSB, which will ensure that all memory write effects affected by the first TLBI have been globally observed. The additional TLBI can use any operation that is broadcast to affected CPUs, and the additional DSB can use any option that is sufficient to complete the additional TLBI. The ARM64_WORKAROUND_REPEAT_TLBI workaround is sufficient to mitigate the issue. Enable this workaround for affected CPUs, and update the silicon errata documentation accordingly. Note that due to the manner in which Arm develops IP and tracks errata, some CPUs share a common erratum number. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon [Mark: backport to v5.10.y] Signed-off-by: Mark Rutland Signed-off-by: Greg Kroah-Hartman Changed files: arch/arm64/kernel/cpu_errata.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=925058203229403008d77a52b1e63e2ae5f4a3cf ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53354 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53354 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:H/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7 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: 7 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).