From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68082][MODERATE 7.0] libceph: fix two unsafe bare decodes in decode_lockers() Date: Sat, 08 Aug 2026 05:54:37 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68082 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 6 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: a54be593d0b749161b08a1e56189b2cb9114267a List-Id: CVE: CVE-2026-68082 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: libceph: fix two unsafe bare decodes in decode_lockers() Commit: a54be593d0b749161b08a1e56189b2cb9114267a Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a54be593d0b749161b08a1e56189b2cb9114267a Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68082 Analysis date: Sat, 08 Aug 2026 05:54:37 -0400 ActionableScore: 6 ActionableScore lower bound: 5 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A malicious or compromised Ceph OSD can send malformed lock.get_info data that triggers slab out-of-bounds reads in libceph decode_lockers, potentially causing kernel crash behavior and limited lock-type semantic influence in affected Ceph kernel clients. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68082 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68082 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-2026-68082 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';CWE-125;*CWE-20;CWE-754;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H';BEST CVSS score: '7';DESCR 'An out-of-bounds read in libceph decode_lockers can occur because ceph_decode_32 and ceph_decode_8 were used without bounds checks after a decoded structure boundary. A malicious or compromised Ceph OSD can return malformed lock.get_info data with struct_len 0 or with the cursor advanced exactly to the end of the buffer, causing slab OOB reads in the kernel client. For the CVSS the PR:N because the attacker does not need privileges on the client host, but must be able to act as a malicious or compromised Ceph OSD or tamper with OSD traffic. The issue is network reachable in Ceph deployments where the client accepts replies from such an OSD, but it is normally limited to internal storage networks rather than the public Internet. Impact is at least denial of service through a kernel crash or bad allocation behavior. The paranoid impact uses C:L/I:L/A:H because the bug is a real OOB read and one decoded byte can influence the lock type discriminator, but there is no strong evidence of an arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 6) YES REMOTE READ OOB INIT ERRORPATH NETWORK LINUS KPANIC KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=6 ActionableScoreLower=5 ## 1. ActionableScore * Conservative score: 5 * Paranoid score: 6 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative score signals: * Remote reachable / network-triggerable: +2 A malicious or compromised Ceph OSD can trigger the bug against a kernel Ceph client by returning malformed `lock.get_info` data. * Memory corruption, weak/indirect corruption candidate: +1 The primitive is a slab out-of-bounds read, not an OOB write or UAF. The decoded values are then used as `num_lockers` and `type`, so this is more than a harmless parser bug. * Reliable kernel crash / strong DoS: +1 The OOB read can lead to KASAN reports, invalid allocation behavior, or kernel crash conditions. * Integrity impact plausible: +1 The one-byte OOB read feeds `*type`, which is used as a lock type discriminator by callers. This gives limited but plausible semantic influence. * Important filesystem/storage path: +1 This affects libceph client handling for Ceph/RBD locking paths, including RBD exclusive lock related flows. * Corruption primitive highly constrained: -1 There is no demonstrated attacker-controlled overwrite, UAF reclaim, arbitrary write, or direct disclosure primitive. Paranoid additional signal: * Confidentiality impact plausible: +1 The bug is a real kernel OOB read. Although no direct user-visible disclosure path is shown, limited confidentiality concern is defensible for manual triage. ## 3. Reachability analysis The likely attacker is a malicious or compromised Ceph OSD, or an actor able to tamper with OSD traffic. The victim does not need local code execution on the client host, so this is not a local-user-only issue. It is network reachable within Ceph deployments, but normally through internal storage networks rather than the public Internet. Namespaces and containers do not materially reduce the client-side kernel impact if the host kernel Ceph client processes the malicious OSD response. The affected path is only relevant on systems using the kernel Ceph client and lock information paths such as RBD exclusive locking, so it is not a default exposure for generic Linux hosts. ## 4. Severity interpretation This is stronger than an ordinary Moderate parser issue because it is network-triggerable inside the Ceph trust boundary and involves kernel slab OOB reads. It does not look like a clear Important-class LPE because the patch shows read-only OOB access, not UAF, OOB write, controlled object replacement, or arbitrary write. The realistic impact is DoS plus limited semantic integrity concern. The paranoid interpretation supports Actionable Moderate handling due to the network-reachable kernel memory-safety primitive. ## 5. One-sentence report phrase A malicious or compromised Ceph OSD can send malformed lock.get_info data that triggers slab out-of-bounds reads in libceph decode_lockers, potentially causing kernel crash behavior and limited lock-type semantic influence in affected Ceph kernel clients. ## 6. Manual review recommendation MANUAL CHECK REQUIRED. Reason: this is a network-reachable kernel OOB read in a storage client trust boundary, with decoded OOB data influencing allocation count and lock type behavior. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: libceph: fix two unsafe bare decodes in decode_lockers() Commit: a54be593d0b749161b08a1e56189b2cb9114267a Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a54be593d0b749161b08a1e56189b2cb9114267a Commit description: decode_lockers() in cls_lock_client.c contains two bare decode operations that allow a malicious or compromised OSD to trigger slab-out-of-bounds reads: 1. ceph_decode_32(p) at the num_lockers field has no preceding bounds check. ceph_start_decoding() accepts struct_len=0 as valid -- the internal ceph_decode_need(p, end, 0, bad) always passes -- so when an OSD sends struct_len=0, ceph_start_decoding() returns success with p == end. The immediately following bare ceph_decode_32(p) then reads 4 bytes past the validated buffer boundary. The garbage value is passed directly to kzalloc_objs() as the locker count. The sibling function decode_watchers() in osd_client.c already uses ceph_decode_32_safe() after its own ceph_start_decoding() call. decode_lockers() was the only site using the bare variant. 2. ceph_decode_8(p) after the decode_locker() loop has no preceding bounds check. If an OSD crafts num_lockers such that the loop advances p exactly to end, the subsequent bare ceph_decode_8(p) reads one byte past the validated buffer boundary. The result is passed directly into *type, which is used as a lock type discriminator by callers, giving an OSD-controlled one-byte OOB read with direct influence over the lock type field. Fix both by replacing bare operations with their safe variants: ceph_decode_32(p) -> ceph_decode_32_safe(p, end, *num_lockers, err_inval) ceph_decode_8(p) -> ceph_decode_8_safe(p, end, *type, err_free_lockers) The goto targets differ intentionally: err_inval: is a new label returning -EINVAL directly. It is used for the pre-allocation failure path where *lockers is not yet allocated and must not be passed to ceph_free_lockers(). err_free_lockers: is the existing label. It is used for the post-allocation failure path where *lockers is allocated and must be freed. ret is set to -EINVAL before ceph_decode_8_safe() so that err_free_lockers returns the correct error code on bounds violation. Without this, err_free_lockers would return a stale ret value (0 from the successful decode_locker() loop), silently swallowing the error. -EINVAL is correct for both failure paths. The data received from the OSD is structurally malformed. -ENOMEM would misrepresent the failure class to callers and to stable@ backporters triaging error paths. Attacker model: a malicious or compromised OSD in a multi-tenant Ceph deployment can trigger this against any kernel client that issues the lock.get_info class method (e.g. during RBD exclusive lock acquisition). [ idryomov: trim changelog, formatting ] Cc: stable@vger.kernel.org Fixes: d4ed4a5 ("libceph: support for lock.lock_info") Signed-off-by: Pavitra Jha Reviewed-by: Viacheslav Dubeyko Signed-off-by: Ilya Dryomov Signed-off-by: Greg Kroah-Hartman Changed files: net/ceph/cls_lock_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=a54be593d0b749161b08a1e56189b2cb9114267a ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68082 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68082 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:L/A:H The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 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: 5 Paranoid ActionableScore: 6 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: YES 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).