From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64375][IMPORTANT] proc: protect ptrace_may_access() with exec_update_lock (FD links) [ Upstream Date: Sat, 25 Jul 2026 12:26:11 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64375 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 7 X-AL-KERNEL-ActionableScore-Lower: 6 X-AL-KERNEL-Commit: 6253dfee5afba536bb54fc6fe6c091c3758fafe1 List-Id: CVE: CVE-2026-64375 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: proc: protect ptrace_may_access() with exec_update_lock (FD links) [ Upstream Commit: 6253dfee5afba536bb54fc6fe6c091c3758fafe1 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6253dfee5afba536bb54fc6fe6c091c3758fafe1 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64375 Analysis date: Sat, 25 Jul 2026 12:26:11 -0400 ActionableScore: 7 ActionableScore lower bound: 6 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A TOCTOU race in procfs link handling can separate `ptrace_may_access()` from the task used to resolve `/proc/pid/fd` and related links, allowing a local attacker to potentially bypass procfs access controls and inspect or access sensitive process resources. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64375 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64375 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: IMPORTANT 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-2026-64375 IMPORTANT CHECK WITH IMPACT FROM ORIG NN LOW 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:N';CWE-367;CWE-362;CWE-863;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N';BEST CVSS score: '6.3';DESCR 'A TOCTOU race in procfs link handling can separate the ptrace_may_access authorization check from the task used to resolve /proc/pid/fd cwd root exe or map_files links. A local user can try to race a task through exec so the access check is made against one credential or exec state while the link target is resolved after the state has changed. For the CVSS the PR:L because reliable triggering requires local code execution or control of a local process that can drive procfs lookups and exec timing. The issue is not network reachable and is triggered through local procfs operations. Impact is mainly unauthorized access to proc link targets or file descriptor magic links, with possible confidentiality and integrity impact if the race exposes privileged process resources. For the paranoid score, choose the highest still defensible interpretation supported by the access control race and procfs fd context, with preference for manual-review sensitivity over autoclosed false negatives.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7) SKIP CVE-2026-64375 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 778c1144771f0064b6f51bee865cceb0d996f2f9 YES NO NO unknown MAYBE DISK IMPROVEONLY LINUS KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=7 ActionableScoreLower=6 ## 1. ActionableScore * Conservative score: 6 * Paranoid score: 7 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Triggered signals: * Local unprivileged trigger: +1 Local users can access procfs paths such as `/proc/pid/fd`, `/proc/pid/cwd`, `/proc/pid/root`, `/proc/pid/exe`, and `map_files` subject to ptrace-style checks. * Security-boundary bypass with practical sensitive-object access: +2 The bug is a TOCTOU race between `ptrace_may_access()` and the actual procfs link resolution. This is an intended Linux security boundary. * Sensitive file / credential / file-descriptor theft primitive: +2 The affected path includes `/proc/pid/fd` magic links. If the race is won, it may expose file descriptors or paths belonging to a process state that should not have passed the ptrace access check. * Practical exploit chain strongly implied: +1 The patch specifically fixes the separation between access check and object resolution by locking with `exec_update_lock`, which strongly implies a real authorization-race chain around exec state changes. * Confidentiality impact plausible: +1 Unauthorized procfs link resolution can disclose paths, executable state, cwd/root, map files, or potentially sensitive file descriptor targets. * Integrity impact plausible: +1 If a writable privileged fd or special fd is exposed through `/proc/pid/fd`, this can become more than read-only disclosure. * Hard or unreliable race / special timing required: -1 Exploitation requires racing procfs access with exec-related task state changes. Not counted: * Generic memory corruption: +0 The patch does not show UAF, OOB write, double free, arbitrary write, or type confusion. * Reliable kernel crash / strong DoS: +0 The main issue is access-control TOCTOU, not crash or resource exhaustion. Call-site confidence: high. The patch shows both the access check and the affected call sites for `proc_pid_get_link()`, `proc_pid_readlink()`, and fd/cwd/root/exe/map_files link handlers. ## 3. Reachability analysis A local user can trigger the relevant procfs operations without needing network access. The realistic attacker needs local code execution and the ability to coordinate procfs lookups with task exec timing, so PR is effectively local unprivileged rather than remote or admin-only. Namespaces and reduced privilege models matter. Container root, uid 0 without `CAP_SYS_PTRACE`, sandboxed service accounts, or processes relying on ptrace and dumpability boundaries may be affected because the bug targets exactly this kind of permission boundary. The affected procfs functionality is broadly available on normal Linux systems. The exploit condition is race-dependent, but the subsystem and access pattern are common. ## 4. Severity interpretation This behaves more like an Important-class security-boundary bypass candidate than an ordinary Moderate correctness bug. It is not memory corruption, and there is no demonstrated arbitrary write or kernel code execution primitive in the patch. However, procfs fd magic links and ptrace permission checks are security-sensitive, and bypassing them can plausibly expose privileged process resources. The conservative score is Actionable Moderate because exploitation requires a race. The paranoid score reaches Strong Important candidate because the affected object class includes privileged fd links and procfs task state, where confidentiality and integrity consequences can be significant. ## 5. One-sentence report phrase A TOCTOU race in procfs link handling can separate `ptrace_may_access()` from the task used to resolve `/proc/pid/fd` and related links, allowing a local attacker to potentially bypass procfs access controls and inspect or access sensitive process resources. ## 6. Manual review recommendation MANUAL CHECK REQUIRED This should not be auto-closed because it is a local procfs authorization race affecting ptrace-protected fd and task-state links, with plausible sensitive fd exposure and security-boundary bypass impact even without memory corruption. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: proc: protect ptrace_may_access() with exec_update_lock (FD links) [ Upstream Commit: 6253dfee5afba536bb54fc6fe6c091c3758fafe1 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6253dfee5afba536bb54fc6fe6c091c3758fafe1 Changed files: fs/proc/base.c fs/proc/fd.c fs/proc/internal.h 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=6253dfee5afba536bb54fc6fe6c091c3758fafe1 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64375 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64375 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:H/I:L/A:N The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N The Best / paranoid CVSS score: 6.3 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: 6 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).