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VulnerabilityPublished

CVE-2025-59835: LangBot · Relative Path Traversal

Affects LangBotSource CVE Database V5

0

Public exploit available · CVSS 8.6 High · fixed in 4.3.5 : patch LangBot as a priority.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 4.0 base score
8.6High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 35% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 4.3.5
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Oct 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: evidence found.

    CVSS exploit maturity: proof of concept public

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

AI-suggested

European organizations should immediately upgrade LangBot to version 4.3.5 or later, where the vulnerability is patched. Until the upgrade is applied, organizations should restrict access to the /api/v1/files/documents endpoint to only highly trusted users and monitor file upload activities closely for suspicious patterns, such as unusual file paths or types. Implement strict input validation and sanitization on file upload paths to prevent directory traversal attempts. Employ application-layer firewalls or runtime application self-protection (RASP) solutions to detect and block malicious file uploads. Conduct regular audits of server directories to identify unauthorized or suspicious files. Additionally, enforce strong authentication and authorization controls to minimize the risk of credential compromise. Organizations should also prepare incident response plans to quickly address any exploitation attempts. Finally, consider isolating LangBot instances in segmented network zones to limit lateral movement in case of compromise.

Description

LangBot is a global IM bot platform designed for LLMs. In versions 4.1.0 up to but not including 4.3.5, authorized attackers can exploit the /api/v1/files/documents interface to perform arbitrary file uploads. Since this interface does not strictly restrict the storage directory of files on the server, it is possible to upload dangerous files to specific system directories. This is fixed in version 4.3.5.

References

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