From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53357][MODERATE 7.0] Bluetooth: fix UAF in l2cap_sock_cleanup_listen() vs l2cap_conn_del() [ Upstream Date: Thu, 02 Jul 2026 09:56:43 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53357 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: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 751de6ec671fe75ad9cf65a0638d2a06b6a5984d List-Id: CVE: CVE-2026-53357 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: Bluetooth: fix UAF in l2cap_sock_cleanup_listen() vs l2cap_conn_del() [ Upstream Commit: 751de6ec671fe75ad9cf65a0638d2a06b6a5984d Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=751de6ec671fe75ad9cf65a0638d2a06b6a5984d Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53357 Analysis date: Thu, 02 Jul 2026 09:56:43 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A confirmed Bluetooth L2CAP race can let an unprivileged local process trigger a use-after-free between listening socket cleanup and HCI disconnect teardown, causing a kernel crash and requiring manual review for possible UAF-based escalation risk. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53357 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53357 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-2026-53357 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-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A use after free exists in the Bluetooth L2CAP listen cleanup path because bt_accept_dequeue can return a child socket without a stable caller reference after unlinking it from the accept queue. A concurrent HCI disconnect can run through hci_rx_work and l2cap_conn_del, free the child socket and its l2cap_chan, and leave l2cap_sock_cleanup_listen using freed objects during listening socket close. For the CVSS the PR:L is used because a local unprivileged process can exercise the Bluetooth socket listen and close path while the disconnect race is triggered. The issue is not scored as directly network reachable because the patch context still requires local socket activity, although a nearby Bluetooth peer may help drive the disconnect side of the race. Impact is at least local denial of service via kernel crash and in the paranoid case may allow confidentiality and integrity impact due to kernel use after free memory corruption. YES REQUIRES MANUAL CHECK.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) YES REMOTE DEADLOCK DANGER INIT RACE UAF NETWORK KPANIC NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1 The commit states that an unprivileged listen/close race can reproduce the issue. * Memory corruption, weak primitive: +1 This is a confirmed KASAN slab use-after-free involving `struct sock` and `l2cap_chan`, but the patch does not show attacker-controlled reclaim, type confusion, arbitrary write, or callback control. * Real lifetime corruption: +1 The bug is a reference/lifetime race where `bt_accept_dequeue()` returns a child socket without a stable caller reference, while `l2cap_conn_del()` can free the same socket and channel. * Reliable kernel crash / strong DoS: +1 The commit includes a KASAN UAF trace and says the race produced multiple UAF reports per run before the fix. Paranoid additional signal: * Firmware-mediated or adjacent external influence: +1 The freeing side is driven by an HCI disconnect path. This is not scored as fully remote reachable, but a nearby Bluetooth peer or controller event may help trigger the disconnect side of the race. Not awarded: * No Remote reachable / network-triggerable +2 The patch context still requires local socket activity and does not establish a purely remote attack. * No strong LPE +2 The UAF is real, but the patch does not demonstrate controlled reclaim, stale callback dispatch, arbitrary write, refcount takeover, or attacker-controlled object replacement. * No hard race penalty Although this is a race, the commit reports repeated KASAN reproductions under SMP testing, so it is not treated as merely theoretical or extremely unreliable. ## 3. Reachability analysis A local unprivileged process can exercise the Bluetooth L2CAP listening socket close path. The competing teardown path is triggered by an HCI disconnect through `hci_rx_work -> l2cap_conn_del()`. This makes the bug local in CVSS-style terms, with possible adjacent Bluetooth assistance, but not a clear network-only remote trigger. Namespaces and containers may matter if Bluetooth socket access is delegated or exposed to less trusted workloads. In typical desktop or embedded systems with Bluetooth enabled, the subsystem is realistic. On servers without Bluetooth hardware or with Bluetooth disabled, exposure is much lower. Call-site confidence: high. The patch shows both the vulnerable caller path and the reference-handling changes in `bt_accept_dequeue()`, L2CAP cleanup, and related Bluetooth accept users. ## 4. Severity interpretation This is more than an ordinary Moderate because it is a confirmed kernel UAF in socket/channel lifetime handling and is reproducible with unprivileged local activity. Realistically, the demonstrated impact is kernel crash or DoS. Theoretical privilege escalation concern exists because the affected objects are kernel heap objects with lifetime corruption, but the patch does not show a concrete exploit primitive beyond UAF. Conservative handling is Actionable Moderate. Paranoid handling reaches Strong Important candidate / Actionable Moderate at minimum because kernel UAFs in reachable local protocol code should not be auto-closed without manual review. ## 5. One-sentence report phrase A confirmed Bluetooth L2CAP race can let an unprivileged local process trigger a use-after-free between listening socket cleanup and HCI disconnect teardown, causing a kernel crash and requiring manual review for possible UAF-based escalation risk. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: confirmed KASAN use-after-free, local unprivileged trigger, socket/channel lifetime corruption, and possible adjacent Bluetooth influence. The known impact is DoS, but kernel UAF class and reachable local trigger make automatic closure unsafe. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: Bluetooth: fix UAF in l2cap_sock_cleanup_listen() vs l2cap_conn_del() [ Upstream Commit: 751de6ec671fe75ad9cf65a0638d2a06b6a5984d Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=751de6ec671fe75ad9cf65a0638d2a06b6a5984d Changed files: net/bluetooth/af_bluetooth.c net/bluetooth/l2cap_sock.c net/bluetooth/rfcomm/sock.c net/bluetooth/sco.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=751de6ec671fe75ad9cf65a0638d2a06b6a5984d ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53357 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53357 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: 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: 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).