From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46185][MODERATE 7.0] smb/client: fix out-of-bounds read in symlink_data() Date: Thu, 28 May 2026 06:22:43 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46185 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: ef6495d4df6e7af8f3de67e65150881c880f696c List-Id: CVE: CVE-2026-46185 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: smb/client: fix out-of-bounds read in symlink_data() Commit: ef6495d4df6e7af8f3de67e65150881c880f696c Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ef6495d4df6e7af8f3de67e65150881c880f696c Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46185 Analysis date: Thu, 28 May 2026 06:22:43 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: NO Summary: A malicious SMB server can send a truncated symlink error response that bypasses length validation and causes an out-of-bounds read in the Linux SMB client, leading primarily to remote server-to-client DoS with limited confidentiality concern. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46185 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46185 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-2026-46185 MODERATE 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:L/I:N/A:H';CWE-125;*CWE-20;CWE-126;Other CVSS 'AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L';BEST CVSS score: '7.1';DESCR 'An out of bounds read in the SMB2 client symlink error handling path can occur because smb2_check_message() accepted STATUS_STOPPED_ON_SYMLINK responses without ensuring that the response length is larger than the calculated SMB2 header length. A malicious or compromised SMB server can return a truncated symlink error response containing only the base SMB2 header, after which symlink_data() may read ErrorContextCount or ByteCount past the received buffer. For the CVSS the PR:N is used for the paranoid score because the attacker only needs to control the SMB server response, while the victim must connect to or use that SMB share. The issue is network reachable from a server to a client and can cause at least denial of service. Worst case is limited confidentiality concern from a kernel out of bounds read, but no write primitive or privilege escalation is shown.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) YES OOB DISK SIMPLEFIX SERVERTOCLIENT 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 * **Remote reachable / network-triggerable: +2** A malicious or compromised SMB server can send a truncated `STATUS_STOPPED_ON_SYMLINK` response to the Linux SMB client. * **Reliable kernel crash / strong DoS concern: +1** The client may read past the received SMB2 buffer in kernel code. The patch shows an OOB read, not a write, but malformed remote responses can plausibly cause kernel fault or instability. * **Important filesystem/storage path: +1** This is in the SMB client filesystem path, affecting remote filesystem access. * **Confidentiality impact plausible, paranoid only: +1** The primitive is an OOB read, so limited adjacent kernel memory exposure is theoretically possible. No clear user-visible disclosure channel is shown, so this is paranoid only. No OOB write, UAF, arbitrary write, or privilege escalation primitive is supported by the patch. ## 3. Reachability analysis The attacker must control or compromise an SMB server, or otherwise cause the victim to connect to a malicious SMB share. The victim side requires SMB client use, so this is server-to-client network exposure with user or system interaction to mount or access the share. Namespaces do not materially reduce the issue if the SMB client runs in the host kernel. The affected code is not triggered by arbitrary inbound packets to the victim, but by malformed SMB responses on an established client connection. ## 4. Severity interpretation This is more than a local low-risk bug because it is remotely supplied protocol input processed by a kernel filesystem client. Realistic impact is most likely DoS from an OOB read. Theoretical confidentiality impact is possible but not proven, and there is no evidence of integrity impact or privilege escalation. This fits **Actionable Moderate** rather than clear Important. ## 5. One-sentence report phrase A malicious SMB server can send a truncated symlink error response that bypasses length validation and causes an out-of-bounds read in the Linux SMB client, leading primarily to remote server-to-client DoS with limited confidentiality concern. ## 6. Manual review recommendation **MANUAL CHECK RECOMMENDED** The bug is network-reachable from a malicious SMB server and involves kernel OOB read parsing, so it should not be auto-closed, although no write primitive or LPE path is shown. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: smb/client: fix out-of-bounds read in symlink_data() Commit: ef6495d4df6e7af8f3de67e65150881c880f696c Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ef6495d4df6e7af8f3de67e65150881c880f696c Commit description: Since smb2_check_message() returns success without length validation for the symlink error response, in symlink_data() it is possible for iov->iov_len to be smaller than sizeof(struct smb2_err_rsp). If the buffer only contains the base SMB2 header (64 bytes), accessing err->ErrorContextCount (at offset 66) or err->ByteCount later in symlink_data() will cause an out-of-bounds read. Link: https://lore.kernel.org/linux-cifs/297d8d9b-adf7-42fd-a1c2-5b1f230032bc@chenxiaosong.com/ Fixes: 76894f3 ("cifs: improve symlink handling for smb2+") Cc: Stable@vger.kernel.org Signed-off-by: Zisen Ye Reviewed-by: ChenXiaoSong Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman Changed files: fs/smb/client/smb2misc.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=ef6495d4df6e7af8f3de67e65150881c880f696c ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46185 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46185 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:L The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H The Best / paranoid CVSS score: 7.1 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).