CVE-2026-40518: ByteDance DeerFlow before commit 2176b2b contains a path traversal and arbitrary file write vulnerability in b

Routine

HIGH 7.1DOWNGRADE

CVE-2026-40518 is a high-severity flaw (CVSS 7.1) affecting deerflow. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 permiss

Why this priority

High severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 71%)
CISA exploited list	No
Weakness	CWE-22
Published	2026-04-17
Last modified	2026-10-26

Publisher (CNA): VulnCheck · Vendor: bytedance

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-17 17:17 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

bytedance deerflow DOWNGRADE

Affected: 2.0-m0

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0-m0

1. Check installed version

apt-cache policy deerflow || rpm -q deerflow || deerflow --version

2. No fixed release: DOWNGRADE to a release before 2.0-m0 (Debian / Ubuntu)

apt-cache madison deerflow sudo apt install deerflow=<VERSION_BEFORE_2.0-m0> sudo apt-mark hold deerflow

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list deerflow sudo dnf downgrade deerflow-<VERSION_BEFORE_2.0-m0> sudo dnf versionlock add deerflow

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40518?

deerflow: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-40518 being exploited?

CVE-2026-40518 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40518 affect?

CVE-2026-40518 affects deerflow. Severity is high (CVSS 7.1). 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 ab

How urgent is CVE-2026-40518?

Priority 32/100. High severity

Software pages

Bootstrap vulnerabilities

Related CVEs

CVE-2026-34430 HIGH 8.8 UPGRADE ByteDance DeerFlow versions prior to commit 92c7a20 contain a sandbox escape vulnerability in bash tool handli

References

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