From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53147][MODERATE 7.0] thunderbolt: Validate XDomain request packet size before type cast Date: Fri, 26 Jun 2026 04:10:55 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53147 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: 2 X-AL-KERNEL-Commit: a770e62923090d7572f1f5a8507ae551d354a057 List-Id: CVE: CVE-2026-53147 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: thunderbolt: Validate XDomain request packet size before type cast Commit: a770e62923090d7572f1f5a8507ae551d354a057 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a770e62923090d7572f1f5a8507ae551d354a057 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53147 Analysis date: Fri, 26 Jun 2026 04:10:55 -0400 ActionableScore: 5 ActionableScore lower bound: 2 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A malicious Thunderbolt or USB4 XDomain peer can send a short request packet that passes generic validation but is smaller than the protocol-specific structure later accessed, causing an out-of-bounds kernel read with possible limited information exposure or host DoS. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53147 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53147 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-2026-53147 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:L/I:N/A:L';BEST CVSS score: '7.1';DESCR 'Thunderbolt XDomain request handling can read past the end of a received kmemdup packet because tb_xdp_handle_request casts the buffer to protocol specific request structures before verifying that the packet is large enough. A malicious XDomain peer can send a minimal packet that passes the generic header length check but is shorter than the structure accessed after the cast, causing an out of bounds kernel read. For the CVSS the PR:N is used because the peer does not need a local user account on the victim once it can send XDomain packets. The base score treats the attack as physical access to a Thunderbolt port, while the paranoid score treats an already connected Thunderbolt or USB4 peer as adjacent. Impact is at least denial of service or limited confidentiality exposure from an invalid kernel read, with no clear evidence of an OOB write or privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) SKIP CVE-2026-53147 SKIP No affected files built, so skip this CVE NO - - unknown MAYBE READ DANGER SIMPLEFIX IMPROVEONLY PACKET INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Paranoid score signals: * Firmware-mediated external influence: +1 A malicious Thunderbolt or USB4 XDomain peer can influence the packet contents processed by the host kernel. * Privileged kernel/device-management path: +1 The bug is in the Thunderbolt XDomain control path, a trusted kernel device-management subsystem processing peer supplied protocol data. * Reliable kernel crash / strong DoS: +1 The malformed packet can drive out-of-bounds reads in kernel request handling. A host-wide crash is plausible depending on slab layout, debug options, and accessed fields. * Confidentiality impact plausible: +1 The primitive is an out-of-bounds kernel read from a kmemdup allocation. There is no proven disclosure channel in the patch, but limited adjacent-memory exposure is plausible. * Availability impact realistic: +1 A malformed peer packet can plausibly destabilize the kernel or cause an oops, especially because this is asynchronous workqueue processing in a hardware protocol path. Conservative deductions: * Physical-only or rare hardware-only condition: -2 In the conservative model, the attacker needs physical access to a Thunderbolt port or control of an attached Thunderbolt or USB4 peer device. Not counted: * Remote reachable / network-triggerable: +0 This is not Internet or normal network reachable. * Local unprivileged trigger: +0 No local user account is needed, but the trigger is not a normal local syscall interface. * Generic memory corruption: +0 The patch supports OOB read only, not OOB write, UAF, double-free, or controlled overwrite. * Privilege escalation plausible: +0 No realistic LPE primitive is demonstrated. * Real lifetime corruption: +0 No lifetime, refcount, RCU, or stale pointer issue is shown. ## 3. Reachability analysis The bug can be triggered by a malicious Thunderbolt or USB4 XDomain peer that can send a short request packet passing the generic header validation but shorter than the protocol-specific structure later accessed. This does not require a local user account on the victim host, but it does require physical or adjacent-device reachability to the Thunderbolt fabric. Namespaces and containers do not materially lower or raise privileges here because the affected path is not a namespace-scoped local API. The practical exposure depends on hardware presence, Thunderbolt/USB4 support, and whether an attacker can attach or control a peer device. This is not a default Internet-facing attack surface. ## 4. Severity interpretation This behaves above an ordinary Moderate issue because it is peer-triggered kernel OOB read in a hardware control protocol. It is not a strong Important candidate on current evidence because the primitive is read-only and the patch does not show UAF, OOB write, arbitrary write, reclaim control, or a clear privilege escalation path. The realistic impact is limited confidentiality exposure and possible DoS. The paranoid score treats the peer as adjacent rather than purely physical and assumes the OOB read can produce a host-visible crash, making it Actionable Moderate and not suitable for automatic closure without review. ## 5. One-sentence report phrase A malicious Thunderbolt or USB4 XDomain peer can send a short request packet that passes generic validation but is smaller than the protocol-specific structure later accessed, causing an out-of-bounds kernel read with possible limited information exposure or host DoS. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a peer-reachable kernel OOB read in a hardware control protocol. The current evidence does not justify LPE or strong memory corruption scoring, but the adjacent-device attack model and possible kernel memory exposure make automatic closure risky. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: thunderbolt: Validate XDomain request packet size before type cast Commit: a770e62923090d7572f1f5a8507ae551d354a057 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a770e62923090d7572f1f5a8507ae551d354a057 Commit description: tb_xdp_handle_request() casts the received packet buffer to protocol-specific structs without verifying that the allocation is large enough for the target type. A peer can send a minimal XDomain packet that passes the generic header length check but is shorter than the struct accessed after the cast, causing out-of- bounds reads from the kmemdup allocation. Plumb the packet length through xdomain_request_work and validate it against the expected struct size before each cast. Fixes: 8e1de70 ("thunderbolt: Add support for XDomain lane bonding") 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/xdomain.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=a770e62923090d7572f1f5a8507ae551d354a057 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53147 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53147 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:L/I:N/A:L 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: 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).