CVE-2026-76236 in stigmem
Summary
by MITRE • 08/19/2026
stigmem-node before 0.9.0a12 contains a cross-tenant broken object level authorization (BOLA) flaw in the RTBF (right-to-be-forgotten) tombstone mechanism. issue_tombstone defaulted the tenant to "default" instead of the caller's tenant, allowing deletion records to be written to the wrong tenant, and the read-suppression path (_get_tombstone_filter and the tombstone scope cache) lacked a tenant_id predicate, so tombstone suppression was applied tenant-blind across fact queries and provenance reads. As a result, a tenant's deletion could be attributed to the wrong tenant and tombstone suppression could either hide facts belonging to other tenants or fail to hide facts within the correct tenant, undermining data isolation and RTBF guarantees. The issue is exploitable only on multi-tenant deployments running the opt-in stigmem-plugin-multi-tenant; single-tenant deployments are unaffected. Fixed in 0.9.0a12.
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Analysis
by VulDB Data Team • 08/19/2026
The vulnerability identified in stigmem-node versions prior to 0.9.0a12 represents a critical failure in multi-tenant data isolation, specifically manifesting as a cross-tenant broken object level authorization flaw within the right-to-be-forgotten tombstone mechanism. This security defect arises from two distinct but related implementation errors that collectively undermine the integrity of tenant-specific data boundaries. The first error involves the issue_tombstone function, which incorrectly defaulted the associated tenant identifier to "default" rather than dynamically assigning it based on the authenticated caller's tenant context. Consequently, when a user initiated a deletion request under the right-to-be-forgotten protocol, the resulting tombstone record was written with an incorrect tenant attribution. This misattribution means that the system records the existence of a deleted object in the wrong logical partition, creating a discrepancy between the actual state of data and its recorded metadata within the multi-tenant architecture.
The second component of this vulnerability lies in the read-suppression logic, which is responsible for ensuring that deleted objects are not returned to users during queries or provenance reads. The functions _get_tombstone_filter and the tombstone scope cache failed to include a tenant_id predicate when evaluating whether an object should be suppressed. This omission results in tenant-blind suppression behavior, where the system applies deletion filters globally rather than restricting them to the specific tenant context of the query. As a result, if a tombstone was incorrectly written for one tenant due to the first flaw, or even if it were correctly written but evaluated without proper scoping, the suppression logic could inadvertently hide facts belonging to other tenants who have not requested deletion. Conversely, in scenarios where the misattribution leads to gaps in coverage, facts within the correct tenant might fail to be hidden when they should be, thereby violating data privacy guarantees and regulatory compliance requirements associated with the right-to-be-forgotten.
The operational impact of this vulnerability is severe for organizations relying on stigmem-node for multi-tenant deployments that utilize the opt-in stigmem-plugin-multi-tenant extension. Single-tenant deployments are unaffected because there is no concept of cross-tenant data leakage in an isolated environment; however, any deployment serving multiple distinct tenants faces significant risks. Attackers with access to one tenant account could potentially exploit this flaw to cause denial-of-service conditions for other tenants by triggering false tombstone suppressions that hide legitimate data from those users. Furthermore, the misattribution of deletion records can lead to audit trail inaccuracies and compliance failures, as regulatory frameworks such as GDPR require precise tracking of when and where personal data is deleted. The inability to guarantee accurate tenant-specific suppression undermines trust in the platform's ability to maintain strict logical separation between tenants, which is a fundamental requirement for secure multi-tenancy.
From a classification perspective, this vulnerability aligns with CWE-639, Authorization Bypass Through User-Controlled Key, as the system fails to properly enforce access control by allowing operations to affect resources outside their intended scope due to improper key handling in the tenant identifier. It also maps to MITRE ATT&CK technique T1530, Data from Information Repositories, specifically regarding the potential for unauthorized data hiding or manipulation that affects availability and integrity rather than just confidentiality. The exploitation of this flaw does not require complex privilege escalation but relies on standard authenticated interactions within a multi-tenant setup, making it particularly dangerous in shared infrastructure environments where trust boundaries are critical.
To mitigate this vulnerability, organizations must upgrade to stigmem-node version 0.9.0a12 or later, which corrects the default tenant assignment logic and enforces strict tenant_id predicates in all tombstone evaluation paths. For deployments that cannot immediately patch due to dependency constraints, implementing a middleware layer that explicitly validates and injects the caller's tenant ID into all deletion requests can serve as an interim control. Additionally, security teams should audit existing multi-tenant configurations to ensure that no residual incorrect tombstones exist from previous operations, potentially requiring data reconciliation scripts to correct any misattributed records. Regular penetration testing focused on cross-tenant isolation and automated unit tests covering edge cases in tenant context propagation are recommended to prevent similar authorization bypasses in future development cycles.