LibreChat Affected by Arbitrary File Write via `execute_code` Artifact Filename Traversal

An attacker exploiting this vulnerability can achieve arbitrary file write access on the LibreChat server. This means they could potentially overwrite critical configuration files, inject malicious code, or even gain remote code execution depending on the permissions of the LibreChat server user. The impact is significant, as it bypasses intended security controls within the execute_code sandbox. The ability to write arbitrary files opens the door to a wide range of attacks, including data exfiltration, denial of service, and complete system compromise. The default local file strategy exacerbates the risk, as it directly concatenates user-supplied filenames into the server-side destination path without proper sanitization.

Organizations deploying LibreChat with the default local file strategy are particularly at risk. Shared hosting environments where multiple users share the same server and have access to the execute_code sandbox are also vulnerable. Legacy LibreChat installations running older versions (prior to 0.8.4) are exposed to this risk.

• nodejs / server:

find /var/lib/librechat -name 'poc.txt' 2>/dev/null

• nodejs / server:

ps aux | grep -i librechat | grep -i 'execute_code'

• generic web: Review access logs for requests to endpoints related to code execution, looking for unusual filenames or patterns indicative of traversal attempts.

1. 2026-04-07Disclosure

   disclosure

1. 已保留2026-03-27
2. 发布日期2026-04-07
3. 修改日期2026-04-08
4. EPSS 更新日期2026-04-15

The primary mitigation for CVE-2026-34371 is to upgrade LibreChat to version 0.8.4 or later, which includes the necessary fix. If upgrading is not immediately feasible, consider implementing a temporary workaround by restricting the executecode sandbox's access to the filesystem. This could involve limiting the directories it can write to or implementing stricter filename validation. Additionally, review server permissions to ensure the LibreChat user has the minimum necessary privileges. Monitoring file system activity for unexpected writes can also help detect potential exploitation. After upgrading, confirm the fix by attempting to trigger the executecode sandbox with a malicious filename containing traversal sequences (e.g., ../../../../../app/client/dist/poc.txt) and verifying that the file is not written.