From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-52954][MODERATE REGULAR] libceph: handle rbtree insertion error in decode_choose_args() Date: Wed, 24 Jun 2026 15:13:34 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-52954 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: 3 X-AL-KERNEL-Commit: c7bf7864e2924fa5508ac270b0e9364bc13d5a6c List-Id: CVE: CVE-2026-52954 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: libceph: handle rbtree insertion error in decode_choose_args() Commit: c7bf7864e2924fa5508ac270b0e9364bc13d5a6c Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c7bf7864e2924fa5508ac270b0e9364bc13d5a6c Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52954 Analysis date: Wed, 24 Jun 2026 15:13:34 -0400 ActionableScore: 4 ActionableScore lower bound: 3 Actionable bucket: Borderline. Manual review required. Actionable Moderate at minimum for exposed Ceph clients Manual review required: YES Summary: A malformed Ceph OSD map with duplicate CRUSH `choose_args_index` values can trigger a reachable kernel `BUG` in libceph rbtree insertion, allowing a malicious or compromised Ceph cluster endpoint to crash affected clients. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52954 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52954 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-2026-52954 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-617;*CWE-20;CWE-755;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'A reachable assertion in libceph CRUSH map parsing can be triggered when a received CEPH_MSG_OSD_MAP contains duplicate choose_args_index values inside choose_args. The second insertion into the choose_args rbtree hits a kernel BUG instead of returning a normal parse error, causing a kernel crash and denial of service for a Ceph client. For the CVSS the PR:N because no local account on the victim is needed if the attacker can make the client accept a crafted OSD map from a malicious or compromised Ceph monitor or through a trusted cluster communication path. The issue is network reachable in Ceph deployments, but practical exploitation usually requires control of a Ceph cluster endpoint or the ability to tamper with authenticated cluster traffic. Impact is denial of service only, with no evidence of memory corruption, information disclosure, or privilege escalation from this patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline. Manual review required. Actionable Moderate at minimum for exposed Ceph clients (with actual score 4) YES REMOTE READ DANGER SIMPLEFIX NETWORK LINUS INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: **3** * Paranoid score: **4** * Final recommended bucket: **Borderline. Manual review required. Actionable Moderate at minimum for exposed Ceph clients** ## 2. Signal breakdown Triggered signals: * **Remote reachable / network-triggerable: +2** The bug is in libceph parsing of `CEPH_MSG_OSD_MAP`, which is received over the Ceph cluster communication path. A malicious or compromised Ceph monitor, or an attacker able to tamper with trusted Ceph traffic, can supply a malformed CRUSH map. * **Reliable kernel crash / strong DoS: +1** Duplicate `choose_args_index` values cause an assertion in the rbtree insertion path, triggering a kernel `BUG`. * **Availability impact realistic: +1, paranoid only** A kernel `BUG` in a kernel Ceph client can cause a host-level denial of service. I count this only in the paranoid score to avoid double-counting the crash signal. Subtract / limiting signals: * **Rare or configuration-dependent exposure: -1, conservative only** This affects systems using the in-kernel Ceph client and accepting OSD maps from a Ceph cluster. It is not a default Internet-facing kernel path on generic Linux systems. Not triggered: * **No generic memory corruption bonus** The patch shows a reachable assertion / validation failure, not UAF, OOB write, double-free, type confusion, or arbitrary write. * **No privilege escalation bonus** There is no demonstrated reclaim, overwrite, stale callback, refcount takeover, or object confusion primitive. * **No confidentiality or integrity impact** The supported impact is kernel crash / DoS only. ## 3. Reachability analysis The issue can be triggered by a crafted or corrupted Ceph OSD map containing duplicate `choose_args_index` values in `choose_args`. A normal local user on the victim does not need an account if the attacker can influence the Ceph monitor side or tamper with accepted Ceph cluster traffic, so this is effectively **PR:N** in that deployment model. In practice, exploitation usually requires a malicious or compromised Ceph monitor, a compromised trusted cluster endpoint, or traffic manipulation inside the Ceph storage network. Ceph clients are common in storage and cloud environments, but this path is not broadly exposed on ordinary Linux systems. Namespaces and containers do not materially reduce the requirement here unless the containerized workload can cause the host kernel Ceph client to connect to attacker-controlled Ceph infrastructure. The main trust boundary is the Ceph cluster communication path, not a local namespace boundary. ## 4. Severity interpretation This behaves like an **actionable Moderate / manual-review DoS issue**, not an Important-class memory corruption issue. The realistic impact is a remotely influenced kernel crash in Ceph deployments where the attacker can control or corrupt an accepted OSD map. The theoretical risk does not extend to LPE or data compromise based on this patch, because the failure mode is an assertion-triggered `BUG` during duplicate-key insertion handling. The paranoid score is higher because network-delivered kernel parser bugs in storage clients deserve scrutiny, especially when they produce a kernel `BUG`. However, the patch context supports DoS only. ## 5. One-sentence report phrase A malformed Ceph OSD map with duplicate CRUSH `choose_args_index` values can trigger a reachable kernel `BUG` in libceph rbtree insertion, allowing a malicious or compromised Ceph cluster endpoint to crash affected clients. ## 6. Manual review recommendation **MANUAL CHECK REQUIRED** Reason: this is a network-delivered kernel parser DoS in libceph, and real exposure depends on Ceph trust boundaries, monitor authentication, and whether affected systems accept OSD maps from potentially compromised cluster endpoints. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: libceph: handle rbtree insertion error in decode_choose_args() Commit: c7bf7864e2924fa5508ac270b0e9364bc13d5a6c Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c7bf7864e2924fa5508ac270b0e9364bc13d5a6c Commit description: A message of type CEPH_MSG_OSD_MAP contains an OSD map that itself contains a CRUSH map. The received CRUSH map may optionally contain choose_args that get decoded in decode_choose_args(). In this function, num_choose_arg_maps is read from the message, and a corresponding number of crush_choose_arg_maps gets decoded afterwards. Each crush_choose_arg_map has a choose_args_index, which serves as the key when inserting it into the choose_args rbtree of the decoded crush_map. If a (potentially corrupted) message contains two crush_choose_arg_maps with the same index, the assertion in insert_choose_arg_map() triggers a kernel BUG when trying to insert the second crush_choose_arg_map. This patch fixes the issue by switching to the non-asserting rbtree insertion function and rejecting the message if the insertion fails. [ idryomov: changelog ] Cc: stable@vger.kernel.org Signed-off-by: Raphael Zimmer Reviewed-by: Ilya Dryomov Signed-off-by: Ilya Dryomov Signed-off-by: Greg Kroah-Hartman Changed files: net/ceph/osdmap.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=c7bf7864e2924fa5508ac270b0e9364bc13d5a6c ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52954 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52954 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:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 7.5 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: 3 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).