From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-52947][MODERATE 7.0] net: qrtr: fix refcount saturation and potential UAF in qrtr_port_remove [ Upstream Date: Thu, 25 Jun 2026 16:51:47 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-52947 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: 7 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 2aa4c12723fe432e623462a3be42a197a128722b List-Id: CVE: CVE-2026-52947 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: net: qrtr: fix refcount saturation and potential UAF in qrtr_port_remove [ Upstream Commit: 2aa4c12723fe432e623462a3be42a197a128722b Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2aa4c12723fe432e623462a3be42a197a128722b Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52947 Analysis date: Thu, 25 Jun 2026 16:51:47 -0400 ActionableScore: 7 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A race in qrtr_port_remove can expose a socket through the QRTR XArray after its reference count has reached zero, creating a local RCU lifetime UAF candidate with demonstrated refcount saturation and possible DoS or privilege escalation risk. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52947 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52947 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-2026-52947 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:H';*CWE-416;CWE-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'qrtr_port_remove can drop the socket reference before removing the port from the qrtr XArray and before the RCU grace period completes. A concurrent RCU reader such as qrtr_reset_ports or qrtr_port_lookup can still obtain the socket pointer and call sock_hold after the refcount reached zero, creating a use-after-free candidate with refcount saturation. For the CVSS the PR:L is used because a local user or local process is normally needed to create and manipulate AF_QRTR sockets, while full administrator privileges are not clearly required once the protocol is available. The issue is not directly reachable over ordinary IP networking. Impact is at least local denial of service via warning, refcount saturation, memory leak, or kernel crash, and in the paranoid case may include privilege escalation because the patch context describes a potential UAF.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6) MAYBE RACE LEAK UAF HARDWARE LINUS KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=7 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 7 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. AF_QRTR socket activity can plausibly be driven by a local process once the protocol is available. * Generic memory corruption: +2. The patch and commit explicitly describe a potential UAF caused by refcount dropping before XArray removal and RCU grace completion. * Real lifetime corruption: +1. This is an RCU lifetime and socket refcount ordering bug. * Reliable kernel crash / strong DoS: +1. syzkaller reached refcount saturation and warning state, with potential leak or crash behavior. * Hard or unreliable race: -1. The issue depends on a concurrent RCU reader racing qrtr_port_remove(). * Rare AND difficult-to-reach subsystem/configuration: -1. QRTR is not a common server-exposed networking path and usually matters on Qualcomm/IPC-router deployments. Paranoid additional interpretation: * Strong LPE plausibility: +2. A socket UAF/refcount lifetime bug can become exploitable if object lifetime and reclaim can be shaped, although no concrete exploit primitive is shown. * Confidentiality impact plausible: +1. Plausible only under the UAF interpretation. * Integrity impact plausible: +1. Plausible only under the UAF interpretation. Paranoid total is capped as an Important candidate because the patch supports a real lifetime/UAF concern, but not a demonstrated arbitrary write or reliable LPE chain. ## 3. Reachability analysis The bug is local, not directly reachable over ordinary IP networking. A local process would need the QRTR protocol available and would need to exercise socket bind/remove or related QRTR port lookup/reset paths while another RCU reader observes the stale XArray entry. Full administrator privileges are not clearly required once AF_QRTR is available, so PR:L is the practical assumption rather than PR:H. The affected subsystem is not broadly exposed on typical generic servers, but it is relevant on systems using Qualcomm IPC Router support. ## 4. Severity interpretation This is not an ordinary low-risk warning cleanup. The ordering bug drops the socket reference before removing the object from the global lookup structure and before waiting for RCU readers, which is a classic lifetime violation. Realistically, the demonstrated impact is refcount saturation, leak, warning, and possible DoS. Theoretical impact is higher because the stale pointer can become a UAF candidate, but the patch does not demonstrate controlled reclaim, object replacement, arbitrary write, or a proven privilege escalation chain. ## 5. One-sentence report phrase A race in qrtr_port_remove can expose a socket through the QRTR XArray after its reference count has reached zero, creating a local RCU lifetime UAF candidate with demonstrated refcount saturation and possible DoS or privilege escalation risk. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a race-based socket lifetime bug with an explicit potential UAF and refcount corruption. Even though realistic exploitation may be difficult and QRTR exposure is deployment-dependent, the bug class is important enough to avoid auto-closure. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net: qrtr: fix refcount saturation and potential UAF in qrtr_port_remove [ Upstream Commit: 2aa4c12723fe432e623462a3be42a197a128722b Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2aa4c12723fe432e623462a3be42a197a128722b Changed files: lib/refcount.c net/qrtr/af_qrtr.c net/socket.c net/qrtr/ns.c init/main.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=2aa4c12723fe432e623462a3be42a197a128722b ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52947 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52947 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:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/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: 4 Paranoid ActionableScore: 7 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).