CVE-2026-77761 misp CVE debrief

Who should care

Organizations using the misp-stix API directly and reusing parser instances across independent STIX documents should be aware of this vulnerability and take necessary actions to prevent potential information contamination. This includes verifying parser implementation, ensuring proper parser state management, and reviewing API usage to prevent parser reuse. Additionally, organizations should monitor for potential information contamination and ensure that proper mitigations are in place to prevent data leakage or incorrect associations in generated threat intelligence.

Technical summary

A parser state isolation vulnerability in misp-stix could cause data from a previously processed STIX document to be retained and incorporated into the MISP event generated from a subsequent document when the same parser instance is reused. Several STIX 1 and STIX 2 parser components maintained per-document state that was not completely cleared between conversions. This issue primarily affects applications using the misp-stix API directly and reusing parser instances across independent STIX documents.

Defensive priority

Organizations using the misp-stix API directly and reusing parser instances across independent STIX documents should verify their implementation and ensure proper parser state management to prevent potential information contamination.

Recommended defensive actions

• Verify parser implementation to ensure proper state management
• Instantiate a new parser for each STIX document
• Review and update API usage to prevent parser reuse
• Monitor for potential information contamination
• Verify affected product deployments exist in managed environments and assign an owner for follow-up
• Review compensating controls for exposed systems while remediation is scheduled and verified
• 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 a parser state isolation vulnerability in misp-stix. The issue arises from the improper clearing of parser state between conversions, potentially leading to information contamination across different STIX documents. Organizations should verify their implementation and ensure proper parser state management to prevent potential information contamination. This may involve reviewing API usage, monitoring for potential information contamination, and ensuring that proper mitigations are in place.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.