From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-43304][IMPORTANT] libceph: define and enforce CEPH_MAX_KEY_LEN [ Upstream Date: Wed, 20 May 2026 19:59:14 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-43304 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: 8 X-AL-KERNEL-ActionableScore-Lower: 6 X-AL-KERNEL-Commit: 6405e8c680974bb74e2c98d5249fb52c7b12a6c6 List-Id: CVE: CVE-2026-43304 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: libceph: define and enforce CEPH_MAX_KEY_LEN [ Upstream Commit: 6405e8c680974bb74e2c98d5249fb52c7b12a6c6 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6405e8c680974bb74e2c98d5249fb52c7b12a6c6 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43304 Analysis date: Wed, 20 May 2026 19:59:14 -0400 ActionableScore: 8 ActionableScore lower bound: 6 Actionable bucket: Strong Important candidate Manual review required: YES Summary: An oversized Ceph authentication key from an attacker-controlled or compromised monitor endpoint can reach fixed libceph messenger v2 auth buffers, creating a kernel memory corruption and crash risk during authentication. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-43304 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43304 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-2026-43304 IMPORTANT CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-121;*CWE-20;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '8.1';DESCR 'libceph accepted key material length from a Ceph authentication reply without enforcing that it fits the fixed session key buffer used by messenger v2 auth completion. A malicious or compromised Ceph monitor endpoint, or an attacker able to tamper with monitor traffic, could provide an oversized key and potentially corrupt kernel memory during auth processing. For the CVSS the PR:N is used because the attacker does not need credentials on the victim if they control or can impersonate the Ceph auth endpoint. The issue is network reachable only in the Ceph monitor/auth path and requires that the client talks to an attacker influenced endpoint, so AC:H is used. Impact is at least denial of service via kernel crash, and worst case may allow confidentiality or integrity impact because the primitive is an oversized network supplied key reaching fixed kernel auth buffers. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate (with actual score 7) YES REMOTE NETWORK LINUS KPANIC NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=8 ActionableScoreLower=6 ## 1. ActionableScore * Conservative score: 6 * Paranoid score: 8 * Final recommended bucket: **Strong Important candidate**:: ## 2. Signal breakdown Conservative score signals: * Firmware or endpoint mediated external influence: +1. The malicious input comes from the Ceph authentication peer, typically a monitor or an attacker able to tamper with that traffic. * Generic memory corruption, strong primitive: +2. The commit explicitly adds a maximum key length because decoded key material must fit a fixed size buffer in `process_auth_done()`. * Reliable kernel crash / strong DoS: +1. Oversized authentication material reaching fixed kernel buffers can plausibly crash the kernel. * Availability impact realistic: +1. A kernel crash in the Ceph client auth path is a system-wide DoS. * Integrity impact plausible: +1. Oversized attacker-influenced key material reaching a fixed buffer is a plausible corruption sink. * Rare/configuration-dependent exposure: -1. This only affects systems using kernel Ceph/libceph clients and messenger v2 authentication with attacker-influenced monitor/auth replies. Paranoid additions: * Remote reachable / network-triggerable interpretation: +1 over conservative. If the attacker controls or impersonates the Ceph monitor/auth endpoint, the trigger is network-delivered and does not require local access on the victim. * Weak privilege-escalation or kernel compromise concern: +1. Fixed-buffer corruption during network authentication is security-sensitive, although no arbitrary write or reliable exploitation primitive is shown. * Confidentiality impact plausible: +1. In worst case, kernel memory corruption during auth processing may create disclosure or broader compromise paths. ## 3. Reachability analysis The attacker is not an arbitrary Internet packet sender in the usual case. They need to control a Ceph monitor/auth endpoint, compromise it, impersonate it, or tamper with Ceph monitor traffic. No local user account on the victim is required in that model. Containers do not materially change the trigger unless they can cause the host kernel Ceph client to connect to attacker-controlled Ceph infrastructure. The path is not default-enabled on all Linux systems, but it is realistic on hosts using CephFS/RBD or other kernel Ceph clients. ## 4. Severity interpretation Conservatively this is an Actionable Moderate because exposure is Ceph-specific and requires attacker influence over the auth peer. Paranoid triage reaches Strong Important candidate because the patch prevents oversized network-supplied key material from reaching fixed kernel authentication buffers, which is a concrete memory corruption pattern. Practical exploitation beyond DoS is not demonstrated, but the bug should not be auto-closed. ## 5. One-sentence report phrase An oversized Ceph authentication key from an attacker-controlled or compromised monitor endpoint can reach fixed libceph messenger v2 auth buffers, creating a kernel memory corruption and crash risk during authentication. ## 6. Manual review recommendation **MANUAL CHECK REQUIRED** Reason: this is network-influenced fixed-buffer memory corruption in kernel Ceph authentication. Exposure is deployment-specific, but the primitive is strong enough to require manual review. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: libceph: define and enforce CEPH_MAX_KEY_LEN [ Upstream Commit: 6405e8c680974bb74e2c98d5249fb52c7b12a6c6 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6405e8c680974bb74e2c98d5249fb52c7b12a6c6 Changed files: net/ceph/crypto.c net/ceph/crypto.h net/ceph/messenger_v2.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=6405e8c680974bb74e2c98d5249fb52c7b12a6c6 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-43304 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-43304 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:L/I:L/A:H The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 8.1 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: 8 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).