CVE-2026-77755 misp CVE debrief

Who should care

Organizations using misp-stix for STIX import workflows should be aware of this vulnerability and take steps to mitigate it. This includes reviewing and updating STIX import workflows to handle parsing and loading failures, implementing input-size limits before parsing STIX documents, and monitoring for and responding to potential denial-of-service attacks. Affected operators, platforms, and security teams should prioritize vulnerability management and ensure that defensive measures are in place to prevent exploitation. This may involve verifying system configurations, applying vendor-provided fixes, and implementing compensating controls for exposed systems while remediation is scheduled and verified. Additionally, tracking exceptions, retesting remediated assets, and documenting evidence are crucial steps in managing this vulnerability effectively. The priority posture for this vulnerability is high due to its potential for denial-of-service attacks, emphasizing the need for prompt action and thorough defensive strategies to mitigate its impact effectively across the organization. This involves a coordinated effort from various teams, including IT operations, security, and management, to ensure comprehensive coverage and minimize potential disruptions to services relying on the converter. By taking proactive measures, organizations can reduce their risk exposure and maintain the integrity and availability of their STIX import workflows. Effective communication and collaboration among stakeholders are essential in addressing this vulnerability and ensuring a robust defense against potential threats. Therefore, it is imperative that organizations assess their current STIX import workflows, identify potential vulnerabilities, and implement necessary controls to prevent exploitation and minimize the risk of denial-of-service attacks. This proactive approach will help safeguard against the potential impacts of this vulnerability and ensure the continued reliability and performance of misp-stix import workflows. The role of security teams in this process is critical, as they must work closely with IT operations and other stakeholders to implement effective defensive

Technical summary

The vulnerability allows an attacker to cause a denial-of-service condition by providing a malformed or large STIX document, potentially terminating or severely degrading the importing service. This is due to the STIX import code using sys.exit() to handle parsing and loading failures, which bypasses exception handlers used by callers of the library. Furthermore, no limit was imposed on the size of STIX documents before parsing, allowing a sufficiently large document to cause excessive memory and CPU consumption. The fixes replace process-terminating sys.exit() calls with catchable exceptions and extend exception handling around the complete STIX detection and conversion process. The importer also now enforces an input-size limit before parsing, with a default maximum of 100 MB that can be adjusted or disabled.

Defensive priority

High priority due to potential for denial-of-service attacks

Recommended defensive actions

• Review and update STIX import workflows to handle parsing and loading failures
• Implement input-size limits before parsing STIX documents
• Monitor for and respond to potential denial-of-service attacks
• Verify and apply vendor-provided fixes
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, but additional information is limited. Defensive verification tasks are necessary to confirm affected systems and validate fixes. Evidence limits and source grounding suggest that defenders should verify the vulnerability in their specific environments, considering factors such as system configurations and potential exposure. Additional review of vendor-provided fixes and compensating controls may be necessary.

Official resources