From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64370][LOW] posix-cpu-timers: Fix pid refcount leak in do_cpu_nanosleep() error path Date: Sat, 25 Jul 2026 06:04:36 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64370 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 2 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: afed3cdc1cca133f804fcf57ff228974f424b23a List-Id: CVE: CVE-2026-64370 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: posix-cpu-timers: Fix pid refcount leak in do_cpu_nanosleep() error path Commit: afed3cdc1cca133f804fcf57ff228974f424b23a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=afed3cdc1cca133f804fcf57ff228974f424b23a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64370 Analysis date: Sat, 25 Jul 2026 06:04:36 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like auto-close candidate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64370 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64370 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: LOW 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-2026-64370 LOW CHECK WITH IMPACT FROM ORIG NN LOW 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-772;*CWE-401;**CWE-400;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 pid reference leak in do_cpu_nanosleep can occur when posix_cpu_timer_create succeeds but the later posix_cpu_timer_set call fails. The error path returned without deleting the partially initialized CPU timer, leaving the pid reference held and preventing normal cleanup of that pid object. For the CVSS the PR:L is used because a local user process is needed to invoke the affected CPU clock nanosleep path and reach the failing set operation. The issue is not network reachable and does not provide a demonstrated UAF, OOB access, information leak, or write primitive. Impact is local denial of service through resource leakage, with base availability impact low and a paranoid availability impact high only under sustained repeated abuse.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like auto-close candidate (with actual score 2) YES SIMPLEFIX LEAK ERRORPATH TIMER HARDWARE LINUS INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 if sustained repeated abuse of the failing path is proven practical * Final recommended bucket: **Ordinary Moderate / Low-like auto-close candidate**:: 2. Signal breakdown * Local unprivileged trigger: +1. A local user process can potentially reach do_cpu_nanosleep through CPU clock nanosleep interfaces. * Availability impact realistic: +1. The leaked pid reference can accumulate and create local resource pressure, but the patch does not show immediate system-wide failure. * Paranoid only, refcount lifetime leak concern: +1. The bug is a pid reference leak, but it is not a UAF, double-free, stale callback, object replacement, or writable stale object primitive. * No generic memory corruption. The fix only adds posix_cpu_timer_del on an error path to release a pid reference. * No privilege escalation signal. No reclaim, overwrite, type confusion, arbitrary write, or sensitive object access is shown. * No remote/network reachability. This is a local syscall/control path. 3. Reachability analysis A local process must invoke the affected POSIX CPU timer nanosleep path and make posix_cpu_timer_set fail after posix_cpu_timer_create has taken a pid reference. Namespaces do not appear to turn this into a cross-boundary issue. The functionality is part of a common kernel time subsystem, but the vulnerable condition is an error path rather than a normal fast path. Realistic exploitation is limited to repeated local triggering for resource leakage. 4. Severity interpretation This behaves like an ordinary Moderate or Low-like resource leak, not an Important-class kernel vulnerability. The theoretical worst case is local DoS through accumulated pid reference leaks. The patch does not support memory corruption, confidentiality impact, integrity impact, or privilege escalation. 5. One-sentence report phrase A local pid reference leak in do_cpu_nanosleep can occur when posix_cpu_timer_set fails after timer creation, potentially causing resource exhaustion under repeated abuse but without evidence of UAF, memory corruption, or privilege escalation. 6. Manual review recommendation NO MANUAL CHECK NEEDED. This is a local refcount/resource leak with no demonstrated memory corruption primitive or security-boundary bypass. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: posix-cpu-timers: Fix pid refcount leak in do_cpu_nanosleep() error path Commit: afed3cdc1cca133f804fcf57ff228974f424b23a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=afed3cdc1cca133f804fcf57ff228974f424b23a Commit description: In do_cpu_nanosleep(), posix_cpu_timer_create() takes a pid reference via get_pid() and stores it in timer.it.cpu.pid. If the subsequent posix_cpu_timer_set() call fails, the function returns immediately without calling posix_cpu_timer_del() to release the pid reference, causing a leak. Fix it by calling posix_cpu_timer_del() before the unlock-and-return on the error path, consistent with the other exit paths in the same function. Fixes: 1da177e ("Linux-2.6.12-rc2") Signed-off-by: WenTao Liang Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260611161738.97043-1-vulab@iscas.ac.cn Signed-off-by: Greg Kroah-Hartman Changed files: kernel/time/posix-cpu-timers.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=afed3cdc1cca133f804fcf57ff228974f424b23a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64370 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64370 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: 2 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: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW 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).