From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68343][MODERATE 7.0] smb: client: validate DFS referral PathConsumed [ Upstream Date: Mon, 10 Aug 2026 18:18:07 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68343 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: 5b439f39f33ec15d319ced3b025e122346fba987 List-Id: CVE: CVE-2026-68343 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: smb: client: validate DFS referral PathConsumed [ Upstream Commit: 5b439f39f33ec15d319ced3b025e122346fba987 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5b439f39f33ec15d319ced3b025e122346fba987 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68343 Analysis date: Mon, 10 Aug 2026 18:18:07 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A malformed SMB DFS referral can provide a PathConsumed value larger than the client search name, causing later DFS path parsing to advance beyond the path buffer and potentially crash the kernel SMB client. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68343 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68343 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-2026-68343 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H';*CWE-20;CWE-125;CWE-126;Other CVSS 'AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H';BEST CVSS score: '8.6';DESCR 'A malformed DFS referral response can set PathConsumed larger than the SMB client search name. Later DFS path parsing may then advance beyond the end of the path string, creating an out-of-bounds read risk and a likely kernel crash on the client side. For the CVSS the PR:N is used because a malicious or compromised SMB DFS server can send the malformed referral without needing privileges on the victim host. The base score uses UI:R because the victim normally has to connect to or use the affected SMB DFS path. The paranoid score uses UI:N for already configured enterprise DFS environments where the client may contact the attacker controlled server automatically. Impact is at least denial of service and may include limited confidentiality or integrity impact from out-of-bounds path parsing, but there is no clear arbitrary write primitive in this patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES DISK INIT SERVERTOCLIENT KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum** ## 2. Signal breakdown * Remote reachable / network-triggerable: +2 A malicious or compromised SMB/DFS server can return a malformed DFS referral response to the SMB client. * Reliable kernel crash / strong DoS: +1 The unchecked PathConsumed value can make later DFS path parsing advance beyond the end of the search name. The most concrete impact is client-side kernel fault or crash. * Important filesystem/storage path: +1 This is in the SMB client filesystem path and affects DFS referral parsing during path resolution. * Broad/common subsystem or broadly deployed exposure: +1, paranoid only SMB/CIFS clients are common in enterprise environments, and DFS referrals may be used automatically once mounts or domain paths are configured. This raises practical triage priority, but exposure still depends on SMB client use. Not counted: * Generic strong memory corruption: +0 The patch supports an out-of-bounds path parsing or OOB read concern, but does not show OOB write, UAF, double free, arbitrary write, type confusion, or attacker-controlled reclaim. * Privilege escalation plausible: +0 No concrete LPE primitive is shown. * Confidentiality / Integrity impact: +0 conservative There is no demonstrated read-back disclosure path or write primitive. Paranoid CVSS may keep C:L/I:L for manual review sensitivity, but ActionableScore should not strongly count it without a clearer primitive. ## 3. Reachability analysis The attacker is a malicious or compromised SMB/DFS server, or an actor able to influence DFS referral responses. No privileges are needed on the victim host in CVSS terms, but the victim client normally needs to connect to or already use the affected SMB/DFS path. This is not a packet-processing bug against any random host. It is a client-side network parser issue. In managed enterprise environments, DFS paths may be configured or contacted automatically, so UI may be lower in practice than in a simple manual-mount scenario. Namespaces and containers are not the main factor here. The relevant exposure is whether the host kernel SMB client is used and whether untrusted SMB/DFS servers can be reached. ## 4. Severity interpretation This is stronger than an ordinary low-risk Moderate because it is a remote parser issue in a filesystem client and can plausibly cause kernel-side OOB path parsing and DoS. It does not reach a strong Important classification on the provided evidence because the patch does not show a write primitive, UAF, object lifetime corruption, type confusion, or a demonstrated information leak. The realistic impact is remote client-side DoS through a malicious SMB/DFS response. The theoretical concern is limited C/I impact from out-of-bounds path parsing, but this remains a manual-review reason rather than proven Important-class exploitation. ## 5. One-sentence report phrase A malformed SMB DFS referral can provide a PathConsumed value larger than the client search name, causing later DFS path parsing to advance beyond the path buffer and potentially crash the kernel SMB client. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: network-reachable client-side parser issue, malformed remote filesystem response, and OOB path parsing risk. The evidence supports Actionable Moderate handling even though a concrete privilege-escalation or arbitrary-write primitive is not shown. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: smb: client: validate DFS referral PathConsumed [ Upstream Commit: 5b439f39f33ec15d319ced3b025e122346fba987 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5b439f39f33ec15d319ced3b025e122346fba987 Changed files: fs/smb/client/misc.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=5b439f39f33ec15d319ced3b025e122346fba987 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68343 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68343 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:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 8.6 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).