CVE-2018-25332

Vulnerability

GitBucket version 4.23.1 contains a critical unauthenticated remote code execution vulnerability. The weakness stems from a combination of a weak secret token generation algorithm (Blowfish encryption key) and insecure file upload functionality. Specifically, the git-lfs endpoint does not properly validate uploaded files, allowing arbitrary JAR files to be placed in the plugins directory. Additionally, an exposed exploit endpoint executes uploaded plugins. This vulnerability requires no authentication and is reachable via the default web interface on port 8080 [1][4].

Exploitation

An unauthenticated attacker can exploit this vulnerability in three steps: first, brute-force the weak Blowfish encryption key used for session tokens (the key is derived from a predictable secret); second, upload a malicious JAR plugin disguised as a valid file via the git-lfs endpoint; third, trigger the plugin execution through an unauthenticated endpoint that runs plugin code. The attacker needs network access to the GitBucket server and can perform the entire attack without any prior authentication or user interaction [1][4].

Impact

Successful exploitation yields full remote code execution on the GitBucket server as the user running the application (typically a non-root system user). The attacker can execute arbitrary operating system commands, read, modify, or delete any files accessible to that user, and potentially pivot to other systems on the network. This results in complete compromise of confidentiality, integrity, and availability of the GitBucket instance [1][4].

Mitigation

No official patch for GitBucket 4.23.1 exists; the vulnerability is present in this specific version. Users should immediately upgrade to a later version of GitBucket that addresses this issue (versions after 4.23.1 incorporate stronger token generation and file upload validation). Until an upgrade can be performed, the recommended workaround is to restrict network access to the GitBucket server (e.g., using a firewall) and disable the plugin system or the git-lfs endpoint if not required. GitBucket is not listed on the CISA Known Exploited Vulnerabilities (KEV) catalog as of publication [3][4].