CVE-2026-104443 in YesWiki
Summary
by MITRE • 10/02/2026
YesWiki before 4.6.7 contains an empty-filter scope bypass in the triples delete API that allows any authenticated user to delete or forge arbitrary semantic triples regardless of ownership. Attackers can send an empty filter to the triples delete endpoint to remove the admins-group membership triple, emptying the admin group and causing a site-wide authorization lockout.
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Analysis
by VulDB Data Team • 10/02/2026
YesWiki versions prior to 4.6.7 are susceptible to a critical access control vulnerability stemming from improper input validation within the semantic web triples deletion API. This flaw represents an empty-filter scope bypass that fundamentally undermines the intended security model of the application's permission system. The underlying technical issue arises because the endpoint responsible for deleting RDF-like triples does not adequately verify whether the provided filter parameters are non-empty or properly scoped before executing the removal operation. Consequently, when a client submits a request with an empty or null filter object, the backend logic interprets this as a valid instruction to proceed with deletion without applying any restrictive conditions on which specific records should be targeted. This lack of validation allows authenticated users to bypass ownership checks and other access control mechanisms that are normally enforced through explicit filtering criteria.
The operational impact of this vulnerability is severe due to its potential for complete administrative takeover or denial of service against the application's management structure. By exploiting the empty-filter scope bypass, an attacker can target specific internal triples that define group memberships within YesWiki's permission system. Specifically, attackers can delete the triple responsible for assigning users to the admin-group. Since this action removes all members from the administrator role without requiring any additional authorization checks beyond basic authentication, it effectively empties the administrative pool of users. This results in a site-wide authorization lockout where no existing user retains elevated privileges, thereby preventing legitimate administrators from managing the wiki content or system settings until manual database intervention occurs.
From a threat modeling perspective, this vulnerability aligns with CWE-284 Improper Access Control and CWE-798 Use of Hard-coded Credentials if the admin group relies on default configurations that are easily targeted. In terms of attack vectors, it falls under MITRE ATT&CK technique T1078 Valid Accounts, as exploitation requires prior authentication but leverages flawed logic to escalate privileges or disrupt availability. The ability to forge arbitrary semantic triples further exacerbates the risk by allowing attackers to inject malicious data structures that could be exploited in subsequent attacks such as cross-site scripting if those triples are rendered unsanitized on client-side interfaces.
Mitigation strategies must prioritize immediate patching of the YesWiki installation to version 4.6.7 or later, where this input validation logic has been corrected to enforce strict filtering requirements for all deletion operations. For environments unable to upgrade immediately, administrators should implement a web application firewall rule that blocks requests to the triples delete endpoint containing empty filter objects or null values in critical parameter fields. Additionally, implementing role-based access control checks at the database level rather than relying solely on application-layer filters can provide defense-in-depth against such logic flaws. Regular auditing of group membership configurations and maintaining out-of-band administrative recovery procedures are also recommended to minimize downtime should an incident occur before remediation is applied.