Understanding Langflow CVE-2026-55255, and why higher CVSS vulnerabilities aren't always the most exploited

On June 25, 2026, the Sysdig Threat Research Team (TRT) observed the first known active exploitation of a CVSS 9.9 "critical" Langflow vulnerability, tracked as CVE-2026-55255. What we saw explains why this vulnerability likely took longer to exploit than its lower-scored sibling vulnerability, tracked as CVE-2026-33017 with a CVSS score of 9.3, which has already been exploited thousands of times. Langflow is an open-source visual framework for building AI agents and retrieval-augmented generation (RAG) pipelines. The Sysdig TRT observed a single operator running CVE-2026-55255, a cross-tenant insecure direct object reference (IDOR), and CVE-2026-33017, an unauthenticated remote code execution (RCE), against the same Langflow instance in the same week. The operator poured sustained effort into the lower-scored RCE and treated the higher-scored IDOR as a two-request afterthought, only adding it to their toolset to cover more exploitation possibilities. That effort allocation is not an accident. It indicates why the RCE vulnerability has been more heavily pursued by threat actors. The 9.3 RCE is widely exploited and in CISA KEV, whereas the 9.9 IDOR has zero reported in-the-wild exploitation. With attackers now optimizing for effort-to-yield, the IDOR exploitation —…