From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-45835][MODERATE 7.0] Bluetooth: L2CAP: Fix null-ptr-deref in l2cap_sock_new_connection_cb() Date: Tue, 26 May 2026 12:52:07 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-45835 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: ab77c8bc30269bee15d917059a66bea48909f5f0 List-Id: CVE: CVE-2026-45835 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: Bluetooth: L2CAP: Fix null-ptr-deref in l2cap_sock_new_connection_cb() Commit: ab77c8bc30269bee15d917059a66bea48909f5f0 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ab77c8bc30269bee15d917059a66bea48909f5f0 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45835 Analysis date: Tue, 26 May 2026 12:52:07 -0400 ActionableScore: 5 ActionableScore lower bound: 3 Actionable bucket: Actionable Moderate at minimum Manual review required: NO Summary: A missing NULL check in Bluetooth L2CAP l2cap_sock_new_connection_cb can allow an adjacent Bluetooth peer to trigger a NULL pointer dereference and crash the kernel when the new connection callback is reached with chan data unset. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45835 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45835 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-45835 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-754;CWE-703;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.5';DESCR 'A NULL pointer dereference can occur in the Bluetooth L2CAP new connection callback because l2cap_sock_new_connection_cb calls lock_sock(parent) after reading parent from chan data without checking whether parent is NULL. An attacker in Bluetooth range may be able to trigger the vulnerable L2CAP path if the target has an exposed or reachable Bluetooth L2CAP service and the channel state reaches a missing parent socket condition. For the CVSS the PR:N is used because the attacker does not need a local account on the target and only needs Bluetooth adjacency to reach the protocol path. The issue is not directly reachable over the public Internet in the usual IP network sense. Impact is denial of service via kernel crash. C and I are not increased because this is a NULL pointer dereference without evidence of UAF, OOB write, or another memory corruption primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) YES REMOTE NULLPTR SIMPLEFIX NETWORK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO guess ====================================================================== 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: * Remote reachable / network-triggerable: +2. Bluetooth L2CAP is externally reachable over an adjacent wireless protocol when Bluetooth is enabled and the relevant L2CAP path is exposed. * Reliable kernel crash / strong DoS: +1. The patch prevents lock_sock(parent) with parent == NULL, which is a direct NULL pointer dereference crash path. * Availability impact realistic: +1. A kernel crash or oops is a realistic availability impact if the path is reachable. * Hard or uncertain triggering condition: -1. The diff proves the missing NULL guard, but does not by itself prove that an unauthenticated peer can reliably force chan->data == NULL in common configurations. Paranoid delta: * No hard-race or timing penalty in the paranoid interpretation. If the L2CAP state can be reached by a malformed or unexpected connection sequence, triggering becomes a practical adjacent DoS. * Broad/common subsystem exposure: +1. Bluetooth is a common kernel subsystem on laptops, desktops, and embedded systems, although not always enabled or listening. Not counted: * Generic memory corruption: +0. This is a NULL pointer dereference, not UAF, OOB write, double free, or type confusion. * Privilege escalation plausible: +0. No reclaim, overwrite, refcount takeover, or object confusion primitive is shown. * Confidentiality/Integrity: +0. No information leak or write primitive is supported by the patch. ## 3. Reachability analysis The likely attacker is a nearby Bluetooth peer, not a local Linux user and not a public Internet attacker. PR:N is reasonable for CVSS-style thinking if the vulnerable L2CAP service is reachable because no local account on the victim is required. Practical reachability depends on Bluetooth being enabled, the host accepting or processing the relevant L2CAP connection path, and whether pairing or service exposure is required in the target deployment. Namespaces and containers are not the main factor here because the interesting attack surface is the host Bluetooth stack. The exploit condition is plausible but not fully demonstrated by the tiny patch, so the conservative score remains borderline while the paranoid score reaches actionable moderate. ## 4. Severity interpretation This behaves like an adjacent-network denial-of-service issue rather than an Important-class memory corruption vulnerability. The theoretical risk is limited because the primitive is a NULL dereference and there is no evidence of UAF, controlled overwrite, page-cache corruption, or privilege escalation. However, Bluetooth is an external wireless attack surface, and a kernel crash reachable from a nearby peer should not be auto-closed without checking the exact L2CAP state machine and exposure requirements. ## 5. One-sentence report phrase A missing NULL check in Bluetooth L2CAP l2cap_sock_new_connection_cb can allow an adjacent Bluetooth peer to trigger a NULL pointer dereference and crash the kernel when the new connection callback is reached with chan data unset. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Reason: the bug is DoS-only based on the patch, but it is in an adjacent wireless protocol path with PR:N-style exposure when Bluetooth L2CAP is reachable. Manual review should confirm whether an unauthenticated or pre-pairing peer can reliably reach the missing-parent state. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: Bluetooth: L2CAP: Fix null-ptr-deref in l2cap_sock_new_connection_cb() Commit: ab77c8bc30269bee15d917059a66bea48909f5f0 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ab77c8bc30269bee15d917059a66bea48909f5f0 Commit description: Add the same NULL guard already present in l2cap_sock_resume_cb() and l2cap_sock_ready_cb(). Fixes: 80808e4 ("Bluetooth: Add l2cap_chan_ops abstraction") Cc: stable@kernel.org Signed-off-by: Siwei Zhang Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Greg Kroah-Hartman Changed files: net/bluetooth/l2cap_sock.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=ab77c8bc30269bee15d917059a66bea48909f5f0 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45835 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45835 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:H/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:N/I:N/A:H The Best / paranoid CVSS score: 6.5 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).