CVE-2026-40518: Bytedance Deerflow

Critical severity, CVSS 9.1. EPSS: 0.5% chance of exploitation in the next 30 days.

ByteDance DeerFlow before commit 2176b2b contains a path traversal and arbitrary file write vulnerability in bootstrap-mode custom-agent creation where the agent name validation is bypassed. Attackers can supply traversal-style values or absolute paths as the agent name to influence directory creation and write files outside the intended custom-agent directory, potentially achieving arbitrary file write on the system subject to filesystem permissions.

Affected products

• Bytedance Deerflow: version 2.0-m0 only

Published 2026-04-17. Last modified 2026-07-14.