Dynatrace Security Researchers discovered CVE-2026-34046, a high-severity broken authorization vulnerability (CVSS 8.7) in Langflow affecting versions up to and including 1.5.0. The flaw resides in the `_read_flow` helper function in the flow management API: when `AUTO_LOGIN` is disabled (i.e., authentication is active), no ownership check is enforced, allowing any authenticated user to read, modify, or delete flows belonging to other users by knowing or guessing a flow UUID. Since Langflow flows often contain embedded API keys and proprietary agent logic, unauthorized read access carries serious consequences. The vulnerability was reported to maintainers on July 8, 2025, fixed the next day but initially disguised as an internal refactor, and formally published as a CVE on March 27, 2026. Remediation requires upgrading to langflow >= 1.5.1 and langflow-base >= 0.5.1.
Table of contents
How Dynatrace detected a zero-day in Langflow prior to public disclosureDisclosure timelineWhat you need to knowWhy timeliness matters for your security coverageHow Dynatrace customers were protectedRemediationQuestions this post answers
What is CVE-2026-34046 in Langflow and how does it work?
CVE-2026-34046 is a broken authorization vulnerability (CVSS 8.7) in Langflow's flow management API. The `_read_flow` helper in `src/backend/base/langflow/api/v1/flows.py` only enforces ownership checks when `AUTO_LOGIN` is enabled. In authenticated multi-user deployments where `AUTO_LOGIN` is disabled, any logged-in user can read, modify, or delete flows belonging to other users simply by knowing or guessing a flow UUID. Flows often contain embedded API keys and proprietary agent logic. Teams running Langflow in production track advisories like this one on daily.dev before they hit public databases.
Which versions of Langflow are affected by CVE-2026-34046 and how do I fix it?
CVE-2026-34046 affects langflow <= 1.5.0 and langflow-base <= 0.5.0. To remediate, upgrade to langflow >= 1.5.1 and langflow-base >= 0.5.1. The fix was committed one day after the vulnerability was reported but was initially labeled as an internal refactor rather than a security fix, delaying the formal advisory by months. Developers upgrading Langflow deployments find breaking security changes faster on daily.dev.