From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80557][MODERATE 7.0] libceph: fix OOB read in decode_watchers() via missing bounds check Date: Wed, 26 Aug 2026 13:49:02 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80557 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1 List-Id: CVE: CVE-2026-80557 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: libceph: fix OOB read in decode_watchers() via missing bounds check Commit: 7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80557 Analysis date: Wed, 26 Aug 2026 13:49:02 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A malicious or compromised Ceph OSD can trigger a 4-byte OOB read in libceph `decode_watchers()` by returning a malformed watcher response with `struct_len=0`, potentially causing kernel client DoS through a bogus watcher count allocation path. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80557 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80557 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 7.0 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-2026-80557 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H';CWE-125;CWE-126;*CWE-20;**CWE-400;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.1';DESCR 'An OOB read in libceph decode_watchers can occur when ceph_start_decoding accepts struct_len 0 and the next ceph_decode_32 reads 4 bytes past the validated response buffer. A malicious or compromised Ceph OSD can trigger this against a kernel client that issues CEPH_OSD_OP_LIST_WATCHERS, and the garbage value can be used as the watcher count for allocation. For the CVSS the PR:N is used because the attacker does not need privileges on the victim host, but does need control of or access to the OSD side of the Ceph storage relationship. The vector is treated as AV:A because Ceph OSD traffic is normally inside a storage or data center network rather than a public Internet service. Impact is at least denial of service via kernel crash or resource exhaustion. For the paranoid score, limited confidentiality impact is kept because this is a real kernel OOB read, but integrity impact is not raised without an OOB write, UAF, or arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES REMOTE OOB NETWORK LINUS DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6 DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Remote reachable / network-triggerable: +2 A malicious or compromised Ceph OSD can send a crafted `obj_list_watch_response_t` reply to a kernel client over the Ceph storage network. * Reliable kernel crash / strong DoS: +1 The 4-byte OOB read can produce a bogus watcher count that is passed to `kzalloc_objs()`, making kernel crash or resource-exhaustion DoS plausible. * Important filesystem/storage path: +1 The bug is in libceph OSD client response parsing, affecting kernel clients in Ceph storage deployments. Paranoid additional signal: * Confidentiality impact plausible: +1 This is a real kernel OOB read past the validated response buffer. No direct disclosure path is shown, so this is limited and only used for the paranoid score. Signals not awarded: * Generic memory corruption: +0 The patch shows OOB read, not OOB write, UAF, double free, type confusion, or arbitrary write. * Privilege escalation plausible: +0 No reclaim, overwrite, callback control, refcount abuse, or object replacement primitive is demonstrated. * Integrity impact plausible: +0 The garbage value influences allocation size, but there is no supported write or ownership-bypass primitive. ## 3. Reachability analysis The realistic attacker is a malicious or compromised Ceph OSD, or an attacker able to tamper with OSD replies in the Ceph storage network. The victim is a Linux kernel Ceph client that issues `CEPH_OSD_OP_LIST_WATCHERS`. This is not a generic public Internet remote bug. It is network-adjacent in typical Ceph deployments, usually inside storage or data-center networks. The attacker does not need privileges on the victim host, so victim-side PR is effectively none, but the attacker must control or influence the OSD side of an established Ceph relationship. Namespaces and containers do not materially lower the trigger requirement unless the containerized workload can cause the host kernel Ceph client to issue the affected operation. ## 4. Severity interpretation This is stronger than an ordinary Moderate because it is network-adjacent protocol parsing in a kernel storage client and fixes a concrete missing bounds check before a kernel read. However, it does not reach a Strong Important candidate by itself because the primitive is a small OOB read with no shown disclosure channel, no write primitive, and no plausible LPE path from the patch context. The conservative interpretation is Actionable Borderline to Moderate due to DoS. The paranoid interpretation is Actionable Moderate because limited confidentiality concern is defensible for a real kernel OOB read in externally influenced response parsing. ## 5. One-sentence report phrase A malicious or compromised Ceph OSD can trigger a 4-byte OOB read in libceph `decode_watchers()` by returning a malformed watcher response with `struct_len=0`, potentially causing kernel client DoS through a bogus watcher count allocation path. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the issue is network-adjacent Ceph response parsing with a real kernel OOB read primitive, and the bogus value affects allocation behavior. Manual review should confirm whether any deployment-specific disclosure, crash reliability, or secondary allocation side effects exist. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: libceph: fix OOB read in decode_watchers() via missing bounds check Commit: 7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1 Commit description: ceph_start_decoding() validates that struct_len bytes remain in the buffer after the encoding header, but accepts struct_len=0 as valid: ceph_decode_need(p, end, 0, bad) always passes. When a malicious or compromised OSD sends an obj_list_watch_response_t reply with struct_len=0, ceph_start_decoding() returns success with p == end, leaving zero bytes guaranteed for subsequent reads. The immediately following ceph_decode_32(p) in decode_watchers() has no preceding bounds check. With p == end this is a 4-byte read past the validated buffer boundary. The garbage value is then passed directly to kzalloc_objs() as the watcher count. The sibling function decode_watcher() already uses the safe variants (ceph_decode_copy_safe, ceph_decode_64_safe, ceph_decode_skip_32) after its own ceph_start_decoding() call. decode_watchers() is the only site that uses the bare variant, confirming an oversight. Fix by replacing ceph_decode_32(p) with ceph_decode_32_safe(p, end, *num_watchers, bad), consistent with the established pattern. Attacker model: a malicious or compromised OSD in a multi-tenant Ceph deployment (e.g. cloud) can trigger this against any kernel client that calls CEPH_OSD_OP_LIST_WATCHERS, without any further privileges beyond OSD session establishment. [ idryomov: trim changelog ] Cc: stable@vger.kernel.org Fixes: a4ed38d ("libceph: support for CEPH_OSD_OP_LIST_WATCHERS") Signed-off-by: Pavitra Jha Reviewed-by: Viacheslav Dubeyko Signed-off-by: Ilya Dryomov Signed-off-by: Greg Kroah-Hartman Changed files: net/ceph/osd_client.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=7130d94846dadbb97b6b7f4d78a3a7bba6e3daa1 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80557 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80557 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:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H The Best / paranoid CVSS score: 7.1 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: 4 Paranoid ActionableScore: 5 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 7.0 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).