Path Traversal and File Write Vulnerability in ByteDance DeerFlow
CVE-2026-40518

7.1HIGH

Key Information:

Vendor

Bytedance

Status
Deer-flow
Vendor
CVE Published:
17 April 2026

What is CVE-2026-40518?

A security flaw exists in ByteDance DeerFlow versions prior to commit 2176b2b, where the creation of custom-agents in bootstrap mode fails to properly validate agent names. This weakness allows an attacker to introduce traversal patterns or absolute paths in the agent name, enabling the potential to create directories and write files outside of the designated custom-agent directory. As a result, this vulnerability could allow unauthorized access to the filesystem, contingent on existing file system permissions.

Affected Version(s)

deer-flow 0 < 2176b2bbfccfce25ceee08318813f96d843a13fd

References

https://github.com/bytedance/deer-flow/pull/2274
issue-tracking
https://github.com/bytedance/deer-flow/commit/2176b2bbfcc...
patch
https://www.vulncheck.com/advisories/bytedance-deerflow-p...
third-party-advisory

CVSS V4

Score:
7.1
Severity:
HIGH
Confidentiality:
None
Integrity:
High
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Chia Min Jun Lennon
.