From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-97561][MODERATE 7.0] smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid Date: Sat, 26 Sep 2026 15:59:43 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-97561 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: unknown X-AL-KERNEL-Commit: e1b74f8f8c1d13190b09fe623b729d36b7ac22a8 List-Id: CVE: CVE-2026-97561 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid Commit: e1b74f8f8c1d13190b09fe623b729d36b7ac22a8 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e1b74f8f8c1d13190b09fe623b729d36b7ac22a8 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97561 Analysis date: Sat, 26 Sep 2026 15:59:43 -0400 ActionableScore: 5 ActionableScore lower bound: unknown Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97561 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97561 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-2026-97561 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-97561 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N';CWE-284;CWE-269;CWE-693;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N';BEST CVSS score: '6.5';DESCR 'An SMB client mount configured with forceuid or forcegid could still accept server supplied SID ownership mappings in several metadata handling paths. A malicious or compromised SMB server can cause files to appear owned by unexpected local users or groups, bypassing the administrators intended ownership policy. This is network reachable after a client mounts an attacker controlled or compromised SMB share with forceuid or forcegid enabled. For the CVSS the PR:N because the remote server does not need privileges on the victim after the vulnerable mount is established. Impact depends on local id mapping and permission checks. It may allow limited confidentiality and integrity impact through incorrect local ownership decisions. This is a policy bypass and no memory corruption or kernel crash is indicated.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) YES DISK IMPROVEONLY SERVERTOCLIENT KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 PrimitiveClass=CLASS_A RealUAF=NO HostAdminRequired=NO NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 5 * Conservative score: 5 * Raw paranoid score: 5 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown * +2 Remote reachable after the SMB mount is established. A malicious or compromised SMB server can supply SIDs through normal metadata responses. * +2 Meaningful ownership policy and security-boundary bypass. The forceuid and forcegid mount policy explicitly requires server supplied ownership to be ignored, but affected paths instead accepted server supplied SID mappings. * +1 Integrity plausible. The server can cause local ownership metadata to differ from the administrator configured uid and gid policy, which can affect local ownership based access decisions. * No UAF, OOB access, arbitrary write, refcount defect, or kernel crash is established. * No Confidentiality point awarded. The patch does not demonstrate a specific protected file read or information disclosure path. * No practical LPE point awarded. The patch establishes an ownership policy bypass, but does not demonstrate local privilege escalation or a complete protected-resource access chain. * No broad filesystem exposure point awarded. SMB client support may be broadly available, but this specific issue additionally requires a mount using forceuid or forcegid. * No negative privilege penalty applied. The remote SMB server does not require host administrative privileges after a vulnerable mount is already established. * No race or timing penalty applies. 3. Reachability analysis The attacker model is a malicious or compromised SMB server serving a share already mounted by the victim with forceuid or forcegid. The affected metadata paths include POSIX stat metadata, directory enumeration metadata, and CIFS ACL ownership mapping. The attacker does not need local code execution or host administrative privileges on the victim after the mount exists. However, practical exposure depends on an administrator or deployment workflow having configured an SMB mount with forceuid and or forcegid. This is not a namespace-scoped capability issue. No special hardware, boot option, or race is required. 4. Primitive and severity interpretation The concrete primitive is a server controlled override of an administrator configured local ownership policy. The mount options are intended to force all remote files to appear as one chosen local uid and gid, but the vulnerable paths overwrite those values through sid_to_id using server supplied ownership SIDs. This is not memory corruption, a lifetime bug, or a crash-only condition. It is a semantic ownership and authorization-boundary bypass affecting local filesystem metadata interpretation. The patch directly restores the intended policy condition by preventing SID to uid and gid mapping when CIFS_MOUNT_OVERR_UID or CIFS_MOUNT_OVERR_GID is set. PrimitiveClass is CLASS_A because the patch establishes a meaningful policy boundary bypass. ImportantCandidate is YES because local ownership metadata can be security relevant and the practical effect depends on CIFS permission behavior, id mapping configuration, mounted-share usage, and local processes that rely on uid and gid ownership checks. AutoDowngradeAllowed is NO because automatically closing the issue as ordinary metadata inconsistency could miss a deployment where ownership confusion enables unintended access or modification. The demonstrated consequence is incorrect local uid and gid ownership representation. A stronger consequence such as protected-file access, local privilege escalation, or confidential-data disclosure remains possible but is not established by the supplied patch alone. 5. One-sentence report phrase An SMB server could bypass forceuid and forcegid mount policy by supplying SID ownership metadata that overwrote the administrator configured local uid and gid values, potentially causing security relevant local ownership confusion. 6. Manual review recommendation MANUAL CHECK REQUIRED Review mounted SMB shares using forceuid or forcegid, local SID to uid gid mapping configuration, CIFS client permission behavior, and whether applications make access-control decisions based on ownership metadata from the mount. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid Commit: e1b74f8f8c1d13190b09fe623b729d36b7ac22a8 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e1b74f8f8c1d13190b09fe623b729d36b7ac22a8 Commit description: When the administrator mounts with forceuid or forcegid (uid=/gid= mount options), they expect all files to appear owned by the specified user/group. However, several code paths unconditionally called sid_to_id() to overwrite cf_uid/cf_gid with server-provided values, ignoring the administrator's explicit override: - smb311_posix_info_to_fattr() (stat via POSIX extensions) - cifs_posix_to_fattr() (readdir via POSIX extensions) - parse_sec_desc() (CIFS ACL ownership mapping) This allowed an untrusted server to dictate local file ownership even when the mount was configured to force specific uid/gid values. Fix all three call sites to check CIFS_MOUNT_OVERR_UID and CIFS_MOUNT_OVERR_GID before calling sid_to_id(), following the same pattern already used by cifs_unix_basic_to_fattr() for unix extensions. Closes: https://sashiko.dev/#/patchset/20260906155816.603278-1-pc%40manguebit.org Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Changed files: fs/smb/client/cifsacl.c fs/smb/client/inode.c fs/smb/client/readdir.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=e1b74f8f8c1d13190b09fe623b729d36b7ac22a8 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97561 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97561 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:H/PR:N/UI:N/S:U/C:L/I:L/A:N The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N 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: unknown 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).