From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68312][MODERATE REGULAR] cifs: fix cifsFileInfo leak on kmalloc failure in deferred close drain paths [ Upstream Date: Mon, 10 Aug 2026 12:07:08 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68312 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: 32390b3f06f26e366cfb27dbac4bc0196c321535 List-Id: CVE: CVE-2026-68312 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: cifs: fix cifsFileInfo leak on kmalloc failure in deferred close drain paths [ Upstream Commit: 32390b3f06f26e366cfb27dbac4bc0196c321535 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=32390b3f06f26e366cfb27dbac4bc0196c321535 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68312 Analysis date: Mon, 10 Aug 2026 12:07:08 -0400 ActionableScore: 3 ActionableScore lower bound: 2 Actionable bucket: Ordinary Moderate / Low-like. Not an Important candidate Manual review required: NO Summary: A CIFS deferred close error path can leak a cifsFileInfo reference and open server handle when allocation fails after deferred work cancellation, allowing local resource exhaustion under memory pressure but not showing memory corruption or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68312 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68312 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-68312 MODERATE 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:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A CIFS deferred close drain path can leak a cifsFileInfo reference and the associated open server handle when cancel_delayed_work() succeeds but the following kmalloc_obj() allocation fails. The failed object is no longer handled by the cancelled deferred work and is also not added to the local processing list, so repeated failures can accumulate resource leaks. For the CVSS the PR:L is used because a local user or process with access to a mounted CIFS share can generate open and close activity without administrative privileges. The issue is not directly reachable by unsolicited network traffic. Impact is primarily denial of service through resource exhaustion under memory pressure, with no UAF or write primitive indicated by the code change.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like. Not an Important candidate (with actual score 3) YES DISK LEAK SERVERTOCLIENT INCREASED_FROM_LOW_TO_MODERATE70_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN3 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 3 * Final recommended bucket: **Ordinary Moderate / Low-like. Not an Important candidate**:: ## 2. Signal breakdown Triggered signals: * Local unprivileged trigger: +1 A local process with access to an already mounted CIFS share can plausibly generate open and close activity that reaches deferred close paths. * Availability impact realistic: +1 The leaked cifsFileInfo reference and open server handle can accumulate under repeated failures and may cause resource exhaustion or degraded CIFS behavior. * Important filesystem/storage path: +1 in paranoid scoring only CIFS is a filesystem client path and leaked open server handles can affect storage/session resources, but this is not metadata corruption or page-cache corruption. Subtracted signals: * Hard or unreliable condition: -1 The bug requires cancel_delayed_work() to succeed and then kmalloc_obj(GFP_ATOMIC) to fail under memory pressure in the deferred close drain path. Not applied: * No generic memory corruption. The patch fixes a missing _cifsFileInfo_put() after allocation failure. It does not show UAF, double free, OOB write, type confusion, stale callback, or refcount takeover. * No privilege escalation plausible. The leaked object is not reused as an attacker-controlled stale pointer and no write or callback primitive is shown. * No remote reachable signal. CIFS is network-backed, but the vulnerable path is client-side local filesystem activity, not unsolicited remote SMB packet parsing. ## 3. Reachability analysis A local user or process that can access a mounted CIFS share may trigger open and close patterns that eventually enter deferred close drain handling. Reliable triggering also depends on memory pressure causing kmalloc_obj(GFP_ATOMIC) failure after deferred work has been cancelled. Namespaces and containers may matter only if a container has access to a host CIFS mount or its own CIFS mount. This does not appear to be directly reachable from a remote SMB server without local client activity. CIFS is common in enterprise environments, but not default-enabled on all systems and requires an active mounted share. Call-site confidence: high, because the affected functions and cleanup consequence are directly visible in the patch. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like resource leak, not an Important-class kernel vulnerability. The theoretical impact is resource exhaustion through leaked cifsFileInfo references and open server handles. Realistic exploitation is constrained by the need for local CIFS access plus allocation failure timing under memory pressure. There is no demonstrated memory corruption primitive, no UAF reclaim, no arbitrary write, no sensitive file disclosure, and no privilege boundary bypass. The paranoid score is slightly higher because sustained repeated failures could produce stronger availability impact, but it should remain below Actionable Moderate. ## 5. One-sentence report phrase A CIFS deferred close error path can leak a cifsFileInfo reference and open server handle when allocation fails after deferred work cancellation, allowing local resource exhaustion under memory pressure but not showing memory corruption or privilege escalation. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be handled as an automatically closable resource leak unless product-specific evidence shows untrusted users can reliably force repeated allocation failures and exhaust CIFS or server resources at scale. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: cifs: fix cifsFileInfo leak on kmalloc failure in deferred close drain paths [ Upstream Commit: 32390b3f06f26e366cfb27dbac4bc0196c321535 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=32390b3f06f26e366cfb27dbac4bc0196c321535 Changed files: fs/smb/client/misc.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=32390b3f06f26e366cfb27dbac4bc0196c321535 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68312 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68312 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:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: 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).