misp-stix EUVD-2026-63850

Exploitation requires that a target MISP instance ingest a STIX document that the attacker can supply or influence - via a configured automated STIX feed, a manual import by an operator, or any integration calling stix_2_to_misp or stix_1_to_misp. For the STIX2 path, the attacker must include MISP-specific tool labels in the bundle to trigger the internal-parser code path and the unfiltered x_misp_attributes copy. For the STIX1 path, the attacker must control the document title field. No authentication is required to craft the STIX document itself; the practical limiting factor is whether the attacker can place content into a feed or submission channel that the target organization actually imports. Impact is confined to manipulation of MISP attribute metadata (distribution, sharing_group_id, tags); code execution is not possible. MISP instances that ingest STIX exclusively from fully controlled, internal sources with no third-party feed intake are not exploitable in practice.

The CVSS 4.0 base score of 6.9 (AV:N/AC:L/AT:N/PR:N/UI:N) accurately represents the networked, low-complexity attack surface; the limited VC:L/VI:L impact metrics reflect that exploitation does not yield code execution or credential access, only metadata manipulation. No EPSS score was provided in the intelligence data, so exploitation probability cannot be quantified numerically. No CISA KEV listing exists, and no POC has been identified, indicating this is not currently under mass exploitation. The real-world risk is primarily organizational and trust-chain oriented: a successful import could silently relabel threat intelligence as publicly distributable, inject attacker-controlled tags that influence automated MISP correlation rules or SOAR playbooks, or corrupt the sharing-group assignments that enforce data-sharing agreements between organizations. Automated STIX feed ingestion - common in operational MISP deployments - removes the need for any user interaction, making the PR:N/UI:N vector realistic without requiring social engineering. The absence of code execution and the requirement to place content into an ingested feed limits the attacker pool, but any organization operating MISP as a central threat-intelligence hub should treat remediation as a priority given the potential to corrupt downstream trust decisions across sharing communities.

An attacker submits a crafted STIX2 bundle to a MISP feed configured for automated ingestion, embedding MISP-specific tool labels that cause the import pipeline to treat the document as an internal MISP re-export. The bundle's x-misp-object entries include extra fields - distribution: 0 (public) and attacker-chosen tags - which are passed verbatim to add_attribute(), writing them into the MISP database. The resulting imported indicators are silently marked as publicly distributable and carry attacker-controlled tags that may trigger downstream SOAR playbooks or corrupt correlation rules across all organizations in the sharing community.