From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53149][MODERATE REGULAR] thunderbolt: Bound root directory content to block size Date: Fri, 26 Jun 2026 05:22:24 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53149 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: 3 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: 5c7657d38d07268124782f03519f07c22a5814fb List-Id: CVE: CVE-2026-53149 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: thunderbolt: Bound root directory content to block size Commit: 5c7657d38d07268124782f03519f07c22a5814fb Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5c7657d38d07268124782f03519f07c22a5814fb Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53149 Analysis date: Fri, 26 Jun 2026 05:22:24 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A missing root directory bounds check in Thunderbolt XDomain property parsing allows malformed peer or device supplied property data to trigger an out of bounds read past the allocated property block, with realistic impact of kernel crash and possible limited confidentiality concern. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53149 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53149 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: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-53149 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H';CWE-125;*CWE-20;CWE-130;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.1';DESCR 'A root directory bounds check was missing in Thunderbolt XDomain property parsing. A malformed property block can make __tb_property_parse_dir() accept content_offset plus content_len beyond block_len, causing the entry parser to read past the allocated property block. For the CVSS the PR:N is used because a malicious Thunderbolt peer or device can provide malformed property data without needing a local account on the victim. The base scenario is physical access to the Thunderbolt or USB4 connection, while the paranoid scenario treats the peer as adjacent on the Thunderbolt fabric. Impact is at least denial of service via kernel crash. Limited confidentiality impact is plausible in the paranoid score because the bug is an out of bounds read, but there is no clear write primitive or supported privilege escalation path from this patch alone.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 3) SKIP CVE-2026-53149 SKIP No affected files built, so skip this CVE NO - - unknown MAYBE OOB INIT SIMPLEFIX IMPROVEONLY DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown * Firmware-mediated external influence: +1 The malformed property block is supplied through Thunderbolt / USB4 XDomain property data from an external peer or device, not by ordinary local syscall input. * Reliable kernel crash / strong DoS: +1 The unchecked root directory length can make the parser read past the allocated property block. This can plausibly cause a kernel fault or parser failure. * Privileged kernel/device-management memory safety path: +1 in paranoid score The bug is in a trusted Thunderbolt device-management parser handling externally influenced device or peer metadata. * Confidentiality impact plausible: +1 in paranoid score only This is an OOB read. Limited data exposure is theoretically possible if out-of-bounds words are interpreted as properties and later surfaced, but the patch does not show a clear disclosure primitive. * Physical-only or rare hardware-only condition: -2 Exploitation requires Thunderbolt / USB4 / XDomain exposure and a malicious or malformed peer/device. This is not Internet remote and not a broad default network path. ## 3. Reachability analysis A malicious Thunderbolt / USB4 peer or device could provide a malformed root directory property block. No local account on the victim is required for that device-side input, so PR is effectively N for CVSS-style reasoning, but physical or adjacent Thunderbolt fabric access is needed. Namespaces and containers do not materially lower or raise reachability because the affected parser is in the host kernel device-management path. The path is only relevant on systems with Thunderbolt / USB4 support and XDomain property handling, so exposure is much narrower than core networking or common local syscall APIs. Realistic exploitation is most credible as a crash or denial of service from a malicious peripheral or peer. A stronger confidentiality outcome is possible enough to justify manual review, but not proven by the diff alone. ## 4. Severity interpretation This behaves like an actionable Moderate issue rather than a clear Important vulnerability. The bug is a kernel OOB read on externally supplied Thunderbolt property data, so it should not be auto-closed as a trivial bounds cleanup. However, there is no OOB write, UAF, double-free, object reclaim primitive, arbitrary write, or strong LPE path shown by the patch. The theoretical memory-safety concern is limited read past the property block. The realistic demonstrated impact is DoS. The paranoid score keeps limited confidentiality concern because OOB read bugs in parsers can sometimes become disclosure paths, but the physical/adjacent hardware requirement keeps this below a Strong Important candidate. ## 5. One-sentence report phrase A missing root directory bounds check in Thunderbolt XDomain property parsing allows malformed peer or device supplied property data to trigger an out of bounds read past the allocated property block, with realistic impact of kernel crash and possible limited confidentiality concern. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a kernel OOB read reachable from externally supplied Thunderbolt / USB4 XDomain property data. It is not clearly exploitable beyond DoS, but the external device-controlled parser input and possible limited disclosure risk make manual review appropriate. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: thunderbolt: Bound root directory content to block size Commit: 5c7657d38d07268124782f03519f07c22a5814fb Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5c7657d38d07268124782f03519f07c22a5814fb Commit description: __tb_property_parse_dir() does not check that content_offset + content_len fits within block_len for the root directory case. When rootdir->length equals or exceeds block_len - 2, the entry loop reads past the allocated property block. Add a bounds check after computing content_offset and content_len to reject directories whose content extends past the block. Fixes: cdae7c0 ("thunderbolt: Add support for XDomain properties") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Michael Bommarito Signed-off-by: Mika Westerberg Signed-off-by: Greg Kroah-Hartman Changed files: drivers/thunderbolt/property.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=5c7657d38d07268124782f03519f07c22a5814fb ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53149 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53149 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:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H The Best / paranoid CVSS score: 7.1 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: 2 Paranoid ActionableScore: 3 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).