From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-45972][IMPORTANT] smb: client: fix potential UAF and double free in smb2_open_file() [ Upstream Date: Wed, 27 May 2026 18:43:48 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-45972 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 8 X-AL-KERNEL-ActionableScore-Lower: 6 X-AL-KERNEL-Commit: 96e53bb3ee2f354cf6b4ab07bcc56e500f8b3f74 List-Id: CVE: CVE-2026-45972 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: NO Patch: smb: client: fix potential UAF and double free in smb2_open_file() [ Upstream Commit: 96e53bb3ee2f354cf6b4ab07bcc56e500f8b3f74 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=96e53bb3ee2f354cf6b4ab07bcc56e500f8b3f74 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45972 Analysis date: Wed, 27 May 2026 18:43:48 -0400 ActionableScore: 8 ActionableScore lower bound: 6 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45972 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45972 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: IMPORTANT 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-2026-45972 IMPORTANT CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H';*CWE-416;CWE-415;CWE-703;*CWE-664;Other CVSS 'AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H';BEST CVSS score: '8.8';DESCR 'smb2_open_file() can free the SMB2_open error response buffer before retrying the open request, but leave err_iov and err_buftype pointing to the old freed state. A malicious or compromised SMB server can trigger the retry path by returning EACCES and then influence later error handling, causing a use after free or double free in the kernel SMB client. For the CVSS the PR:N is used because no privileges are required on the victim once the client connects to the attacker controlled SMB server, while UI:R reflects that a user or system action normally has to access the SMB share. The issue is network reachable from the server side, but it is not a generic unauthenticated packet parser against arbitrary hosts. Impact is at least denial of service via kernel crash and in the worst case may allow confidentiality or integrity impact due to memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8) MAYBE DISK LEAK UAF SERVERTOCLIENT INCREASED_TO_HIGH_BASED_ON_GUESSCVSS8.5PLUS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=8 ActionableScoreLower=6 1. ActionableScore * Conservative score: 6 * Paranoid score: 8 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: 2. Signal breakdown * Remote/server-side reachable: +2. A malicious or compromised SMB server can influence client responses once the victim connects. * Generic memory corruption, strong primitive: +2. The commit explicitly fixes a potential UAF and double free. * Real lifetime corruption: +1. `err_iov` and `err_buftype` retain stale freed response-buffer state across an SMB2 open retry. * Reliable kernel crash / strong DoS: +1. UAF or double free in the kernel SMB client can crash the system. * Paranoid LPE / C/I concern: +1. UAF/double-free in a network filesystem client may be exploitable beyond DoS, though no controlled reclaim primitive is demonstrated. * User interaction required: practical caveat. The victim normally must mount or access an attacker-controlled SMB share. * Not a generic unauthenticated remote kernel parser. Exposure depends on client-initiated SMB access. 3. Reachability analysis The vulnerable path is reached when the Linux SMB client performs `SMB2_open()` and retries after `EACCES` with `retry_without_read_attributes`. A malicious SMB server can shape responses to hit this path, but the victim must connect to or access that server or share. No local privileges are required on the victim after the connection is established. Containers may be relevant if they can trigger host SMB mounts or access kernel CIFS mounts. 4. Severity interpretation This is a strong Important candidate in paranoid triage because it is explicit memory corruption in a network filesystem client influenced by a remote server. Conservative handling is still Actionable Moderate because user/system action is needed to access the share. The realistic minimum impact is kernel crash, while confidentiality or integrity impact is plausible from UAF/double-free but not proven by the patch alone. 5. One-sentence report phrase A malicious SMB server can trigger an `SMB2_open()` retry path that reuses stale freed error-buffer state in the Linux SMB client, causing UAF or double-free memory corruption. 6. Manual review recommendation MANUAL CHECK REQUIRED. The patch fixes explicit UAF/double-free in a remote-server-influenced SMB client path, making it unsuitable for automatic closure as DoS-only. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: smb: client: fix potential UAF and double free in smb2_open_file() [ Upstream Commit: 96e53bb3ee2f354cf6b4ab07bcc56e500f8b3f74 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=96e53bb3ee2f354cf6b4ab07bcc56e500f8b3f74 Changed files: fs/smb/client/smb2file.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=96e53bb3ee2f354cf6b4ab07bcc56e500f8b3f74 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45972 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45972 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:L/PR:N/UI:R/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 8.8 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: 6 Paranoid ActionableScore: 8 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: IMPORTANT KPANIC detected for this report: NO Published priority for this report (same as in Subject): IMPORTANT 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).