From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53188][MODERATE 7.0] RDMA/core: Validate the passed in fops for ib_get_ucaps() Date: Thu, 25 Jun 2026 07:50:27 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53188 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: 3 X-AL-KERNEL-Commit: 96b6e98ff12d50ed5817230c6f1188e1150d225d List-Id: CVE: CVE-2026-53188 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: RDMA/core: Validate the passed in fops for ib_get_ucaps() Commit: 96b6e98ff12d50ed5817230c6f1188e1150d225d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=96b6e98ff12d50ed5817230c6f1188e1150d225d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53188 Analysis date: Thu, 25 Jun 2026 07:50:27 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: RDMA UCAP fd validation relied only on dev_t, allowing a local user with a suitable char/block dev_t alias to masquerade a non UCAP fd as an authentic UCAP cdev and potentially bypass RDMA capability checks. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53188 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53188 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-2026-53188 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N';CWE-863;CWE-284;CWE-287;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N';BEST CVSS score: '6.3';DESCR 'RDMA UCAP validation accepted a file descriptor based only on the numeric dev_t value. A local user could potentially pass a non UCAP device fd with the same dev_t because character and block device numbers can alias, causing the fd to masquerade as an authentic UCAP cdev fd. For the CVSS the PR:L is used for the paranoid score because exploitation requires local code execution and access to a suitable device fd, but does not necessarily require full administrator privileges. The issue is not network reachable and is triggered through a local RDMA control path. Impact is primarily an access control or capability validation bypass. In the worst defensible case, incorrect UCAP acceptance may expose RDMA capabilities with confidentiality or integrity impact and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES SIMPLEFIX NETWORK HARDWARE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. The issue is triggered through a local fd passed to the RDMA UCAP path. * Cross-boundary isolation or policy bypass: +1. The bug bypasses the intended authenticity check for UCAP character-device fds by relying only on dev_t. * Integrity impact plausible: +1. A masqueraded fd may cause incorrect UCAP capability acceptance and affect RDMA capability decisions. * No memory corruption: +0. The patch shows validation of f_ops, not UAF, OOB, double-free, refcount misuse, or arbitrary write. * Not network reachable: +0. This is a local control path, not packet-triggered. Paranoid additional signals: * Security-boundary bypass with practical sensitive-object access: +2 instead of only +1 policy-bypass weighting. UCAP is a capability-gating API, and accepting a non-UCAP fd as authentic may cross an intended permission boundary. * Confidentiality impact plausible: +1. If the wrong UCAP mask exposes RDMA capabilities, sensitive RDMA objects or device capabilities may become visible or usable. * Practical exploit chain strongly implied: +1. The commit explicitly describes a concrete masquerade condition using char/block dev_t aliasing. * Special condition / constrained reachability: -1. Exploitation depends on finding or opening a block device with a colliding dev_t and on affected RDMA UCAP deployment. ## 3. Reachability analysis A local process that can call the affected RDMA UCAP interface and provide an fd can trigger the validation flaw. The attacker does not need remote network reachability, and this is not a packet-processing bug. The required privilege is best treated as local user level for triage because the attacker may only need access to a suitable fd, not full host root. In some deployments access to block devices or RDMA device nodes may be restricted by permissions, cgroups, containers, or device ACLs, which reduces practical reachability. Namespaces and containers matter because device-node exposure can differ from the host. A container or service account with delegated device access may not be fully privileged, so treating this as PR:H would likely understate the practical security-boundary issue. The path is not as broadly exposed as core networking or common filesystems, but RDMA uverbs deployments are security-sensitive when present. ## 4. Severity interpretation This behaves more like an actionable access-control / capability-confusion bug than a generic memory-safety vulnerability. There is no evidence of memory corruption or direct LPE from the patch. The realistic impact depends on what UCAP capabilities can be incorrectly accepted after fd masquerading. The conservative result is borderline Moderate because the exploit condition is specific and local. The paranoid result reaches Actionable Moderate because the bug crosses an intended RDMA capability boundary and may affect confidentiality or integrity depending on deployed UCAP policy. ## 5. One-sentence report phrase RDMA UCAP fd validation relied only on dev_t, allowing a local user with a suitable char/block dev_t alias to masquerade a non UCAP fd as an authentic UCAP cdev and potentially bypass RDMA capability checks. ## 6. Manual review recommendation MANUAL CHECK REQUIRED. The patch is not memory corruption, but it is a capability-boundary validation bug in RDMA core. The real severity depends on what an accepted UCAP mask enables in affected deployments, so it should not be auto-closed without subsystem-aware review. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: RDMA/core: Validate the passed in fops for ib_get_ucaps() Commit: 96b6e98ff12d50ed5817230c6f1188e1150d225d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=96b6e98ff12d50ed5817230c6f1188e1150d225d Commit description: Sashiko pointed out it is not safe to rely only on the devt because char/block alias so if the user finds a block device with the same dev_t it can masquerade as a ucap cdev fd. Test the f_ops to only accept authentic cdevs. Link: https://patch.msgid.link/r/0-v1-fd9482545e37+1e25-ib_ucaps_fd_ops_jgg@nvidia.com Cc: stable@vger.kernel.org Fixes: 61e5168 ("RDMA/uverbs: Introduce UCAP (User CAPabilities) API") Signed-off-by: Jason Gunthorpe Signed-off-by: Greg Kroah-Hartman Changed files: drivers/infiniband/core/ucaps.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=96b6e98ff12d50ed5817230c6f1188e1150d225d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53188 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53188 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:L/UI:N/S:U/C:L/I:L/A:N The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N The Best / paranoid CVSS score: 6.3 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: 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).