CVE-2026-40518Public exploitNetwork attack vector

Arbitrary file write via unvalidated custom-agent names

Published Apr 17, 2026 · Updated Apr 17, 2026

Path traversal in ByteDance DeerFlow before commit 2176b2b allows remote authenticated users to write files outside the agents directory. In bootstrap mode, make_lead_agent() skips load_agent_config() validation, and setup_agent() passes runtime.context["agent_name"] to paths.agent_dir() before creating directories and writing config.yaml or SOUL.md. A low-privileged network session must reach custom-agent creation; writable target paths determine whether configuration is altered or the service is interrupted.

CVSS severity7.1
High
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in ByteDance DeerFlow before commit 2176b2b allows remote authenticated users to write files outside the agents directory. In bootstrap mode, make_lead_agent() skips load_agent_config() validation, and setup_agent() passes runtime.context["agent_name"] to paths.agent_dir() before creating directories and writing config.yaml or SOUL.md. A low-privileged network session must reach custom-agent creation; writable target paths determine whether configuration is altered or the service is interrupted.

The record

CVE
CVE-2026-40518
Published
Apr 17, 2026
Updated
Apr 17, 2026
Vendor
ByteDance
Product
DeerFlow
Classifications
CWE-22, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 17, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <2176b2bbfccfce25ceee08318813f96d843a13fd

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

ByteDance · DeerFlowversion=0 <2176b2bbfccfce25ceee08318813f96d843a13fd

Published CVSS scores

7.1VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
7.1VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1565.001Stored Data Manipulation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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