CVE-2026-40518 HIGH

CVE-2026-40518: ByteDance DeerFlow Path Traversal and Arbitrary File Write via Bootstrap Mode

Vendor Bytedance
Product deer-flow
Weakness CWE-22 · Path traversal
Published April 17, 2026
Last update April 17, 2026

CVSS base score

7.1/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

April 17, 2026 CVE published
April 17, 2026 Record updated