CVE-2026-40518

ByteDance DeerFlow Path Traversal and Arbitrary File Write via Bootstrap Mode

7.1 High

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: High
Availability: Low

Exploit likelihood

0.36%Up 0.3 points since Apr 18, 2026

What each source reports

CVE List Score used 7.1

ByteDance DeerFlow Path Traversal and Arbitrary File Write via Bootstrap Mode

Record: CVE-2026-40518
CVSS 4.0: 7.1 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
CVSS 3.1: 7.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
Weakness: CWE-22
Updated: 2026-11-02

EUVDEUVD-2026-23456 7.1

Record: EUVD-2026-23456
CVSS 4.0: 7.1 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-54pv-34f9-m4mq 7.1

ByteDance DeerFlow before commit 2176b2b contains a path traversal and arbitrary file write...

Record: GHSA-54pv-34f9-m4mq
CVSS 4.0: 7.1 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1: 7.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
Weakness: CWE-22
Updated: 2026-11-02

NVD 7.1

Record: CVE-2026-40518
CVSS 4.0: 7.1 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1: 7.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
CVSS 3.1: 9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Weakness: CWE-22
Updated: 2026-11-02

OSV 7.1

ByteDance DeerFlow Path Traversal and Arbitrary File Write via Bootstrap Mode

Record: CVE-2026-40518
CVSS 4.0: 7.1 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
Weakness: CWE-22
Updated: 2026-11-02

Affected products

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-40518 is a high vulnerability (CVSS 7.1) in Bytedance Deerflow, published April 17, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.36%, the 29th percentile. No source names a fixed version.