Path Traversal in Bytedance Deer-Flow
CVE-2026-40518
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.
Vulnerability class: Path Traversal (Directory Traversal)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H.
EPSS exploit prediction
EPSS: 0.005 (43.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 43.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.002
Affected products
- Bytedance Deer-Flow — versions 0
- Bytedance Deerflow — versions 2.0-m0
Weakness classification (CWE)
References
- github.com/bytedance/deer-flow/pull/2274 (issue-tracking, Patch, Issue Tracking)
- github.com/bytedance/deer-flow/commit/2176b2bbfccfce25ceee08318813f96d843a13fd (Patch, patch)
- www.vulncheck.com/advisories/bytedance-deerflow-path-traversal-and-arbitrary-fi… (Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-40518?
- CVE-2026-40518 is a high-severity vulnerability in Bytedance Deer-Flow, classified under Path Traversal. CVSS score: 7.1/10. Published 2026-04-17.
- How severe is CVE-2026-40518?
- High severity. CVSS v3 base score is 7.1 out of 10.