From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68153][MODERATE REGULAR] libceph: remove debugfs files before client teardown Date: Mon, 10 Aug 2026 13:28:10 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68153 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: 4 X-AL-KERNEL-ActionableScore-Lower: 1 X-AL-KERNEL-Commit: fc1010e7e0204ece6cc0f9af4f473e9553535eab List-Id: CVE: CVE-2026-68153 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: libceph: remove debugfs files before client teardown Commit: fc1010e7e0204ece6cc0f9af4f473e9553535eab Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fc1010e7e0204ece6cc0f9af4f473e9553535eab Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68153 Analysis date: Mon, 10 Aug 2026 13:28:10 -0400 ActionableScore: 4 ActionableScore lower bound: 1 Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: A local race in libceph client teardown can let a debugfs monmap read run after monc monmap is freed, causing a use after free with likely kernel crash and possible limited stale memory exposure. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68153 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68153 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-2026-68153 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race in libceph client teardown can allow a debugfs monmap read handler to run after ceph_monc_stop has freed monc monmap. This creates a use after free in a local debugfs callback and can plausibly cause a kernel crash or limited exposure of stale kernel memory through the show path. For the CVSS the PR:L is used in the paranoid score because some deployments may expose debugfs access or Ceph client teardown control to a local service account, container root, or reduced capability root rather than only to a full administrator. The issue is not directly network reachable because the trigger is local debugfs access racing client destruction, although it affects systems using Ceph client infrastructure. Impact is at least local denial of service via kernel crash and in worst case may allow limited confidentiality or integrity impact due to UAF memory corruption and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3) YES REMOTE RACE UAF NETWORK DEBUGFS LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=1 ## 1. ActionableScore * Conservative score: 1 * Paranoid score: 4 * Final recommended bucket: **Borderline, manual review recommended** ## 2. Signal breakdown Conservative signals: * Memory corruption, weak primitive: +1. The patch describes a race based UAF in monmap_show after monc->monmap is freed. * Real lifetime corruption: +1. This is a stale pointer after free during client teardown. * Reliable kernel crash / strong DoS: +1. A debugfs read racing teardown can plausibly crash the kernel. * Hard or unreliable race / special timing required: -1. Triggering requires concurrent debugfs access and Ceph client teardown. * Requires admin/root/CAP in typical deployments: -2. debugfs access and Ceph client teardown are normally administrator controlled. Paranoid additional interpretation: * Local unprivileged or reduced privilege trigger concern: +1. Some environments may expose debugfs reads or Ceph lifecycle operations to a service account, container root, or reduced capability root. * Confidentiality impact plausible: +1. Because the UAF occurs in a debugfs show path, limited stale kernel data exposure is plausible, although not strongly demonstrated. * No Strong LPE plausibility is awarded. The patch does not show attacker controlled reclaim, object replacement, write after free, type confusion, callback hijack, or refcount takeover. Race-UAF downgrade applied: this is treated as weak UAF rather than strong corruption because the patch only fixes ordering between debugfs removal and client teardown. ## 3. Reachability analysis The trigger is local. An attacker needs to read the per client Ceph monmap debugfs file while another path destroys the Ceph client. In normal deployments, debugfs is root accessible and client teardown usually requires administrative control such as unmounting or stopping the Ceph client. Namespaces or containers could reduce the practical privilege barrier only if debugfs or Ceph management is delegated into that environment. The issue is not network reachable by itself, even though it affects Ceph infrastructure. Call-site confidence: high. The patch directly changes ceph_destroy_client ordering and the commit message identifies monmap_show, ceph_monc_stop, and debugfs_remove lifetime semantics. ## 4. Severity interpretation This behaves like a local race based UAF with realistic DoS impact and limited possible information exposure. It is not an Important candidate by default because exploitation normally requires privileged local access and no strong LPE primitive is shown. It should not be treated as a pure cleanup either, because the bug is a real UAF in a kernel debugfs callback. Theoretical memory corruption potential exists due to UAF. Realistic exploitation evidence supports crash or limited stale read, not reliable privilege escalation. ## 5. One-sentence report phrase A local race in libceph client teardown can let a debugfs monmap read run after monc monmap is freed, causing a use after free with likely kernel crash and possible limited stale memory exposure. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: this is a real race based UAF, but the conservative score remains low because normal triggering requires privileged debugfs and Ceph teardown access. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: libceph: remove debugfs files before client teardown Commit: fc1010e7e0204ece6cc0f9af4f473e9553535eab Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fc1010e7e0204ece6cc0f9af4f473e9553535eab Commit description: ceph_destroy_client() tears down the monitor client before removing the per-client debugfs files. A concurrent read of the monmap debugfs file can enter monmap_show() after ceph_monc_stop() has freed monc->monmap, triggering a use-after-free. Remove the debugfs files before stopping the OSD and monitor clients. debugfs_remove() drains active handlers and prevents new accesses, so the debugfs callbacks can no longer race the rest of client teardown. Cc: stable@vger.kernel.org Fixes: 76aa844 ("ceph: debugfs") Reported-by: Yuan Tan Reported-by: Zhengchuan Liang Reported-by: Xin Liu Assisted-by: Codex:GPT-5.4 Signed-off-by: Douya Le Signed-off-by: Ren Wei Reviewed-by: Viacheslav Dubeyko Signed-off-by: Ilya Dryomov Signed-off-by: Greg Kroah-Hartman Changed files: net/ceph/ceph_common.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=fc1010e7e0204ece6cc0f9af4f473e9553535eab ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68153 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68153 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:H/UI:N/S:U/C:L/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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: 1 Paranoid ActionableScore: 4 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).