# CVE-2026-58166: OpenBMB ChatDev path traversal in file upload handler

Source: https://junglewise.ai/threats/cve-2026-58166-openbmb-chatdev-path-traversal-in-file-upload-handler  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-30. Updated: 2026-06-30  
License: CC BY 4.0 with a link back

CVE-2026-58166 · Severity: critical · CVSS 9.1 · Published 2026-06-30

OpenBMB ChatDev, a platform for AI-driven software development, contains a security flaw in its file upload system. An unauthenticated attacker can exploit this to write or delete any file on the server's filesystem. This could lead to a complete system takeover by overwriting critical configuration files or a total loss of data through arbitrary file deletion.

Vendors: [OpenBMB](https://junglewise.ai/threats/vendors/openbmb).

## Quick answers

**Is CVE-2026-58166 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-58166 being exploited in the wild.

**How severe is CVE-2026-58166?** Critical severity, with a CVSS score of 9.1, published 30 June 2026.

**Which products and versions are affected?** OpenBMB ChatDev through 2.2.0.

**Is there a fix for CVE-2026-58166?** A patch was published on 2026-06-29: Fix merged in commit 4fd4da6 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-58166 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-58166?** Check whether you run OpenBMB ChatDev at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A path traversal vulnerability exists in the `save_upload_file` function within `server/services/attachment_service.py`. The application fails to sanitize the client-provided multipart filename before joining it with a temporary directory path. An unauthenticated attacker can send a POST request to the `/api/uploads/{session_id}` endpoint with a filename containing traversal sequences (e.g., `../../`). This causes the application to write uploaded content to an arbitrary location and subsequently delete the same file during the `finally` cleanup block's `unlink()` operation. The vulnerability is exploitable without authentication as session IDs are minted freely by the workflow server. A fix is available in commit 4fd4da6.

## Affected products

- OpenBMB ChatDev through 2.2.0

## Timeline

- 2026-06-12: disclosed: Issue reported to vendor via GitHub
- 2026-06-29: patched: Fix merged in commit 4fd4da6
- 2026-06-30: advisory: CVE-2026-58166 published

## References

- [https://github.com/OpenBMB/ChatDev/commit/4fd4da603801766b14ad8788649cfc1ad21f99a6](https://github.com/OpenBMB/ChatDev/commit/4fd4da603801766b14ad8788649cfc1ad21f99a6)
- [https://github.com/OpenBMB/ChatDev/issues/638](https://github.com/OpenBMB/ChatDev/issues/638)
- [https://github.com/OpenBMB/ChatDev/pull/641](https://github.com/OpenBMB/ChatDev/pull/641)
- [https://www.vulncheck.com/advisories/openbmb-chatdev-unauthenticated-path-traversal-in-upload-handler-allows-arbitrary-file-write-and-delete](https://www.vulncheck.com/advisories/openbmb-chatdev-unauthenticated-path-traversal-in-upload-handler-allows-arbitrary-file-write-and-delete)