CVE-2018-25332: GitBucket 4.23.1 RCE Vulnerability

CVE-2018-25332 Overview

CVE-2018-25332 is an unauthenticated remote code execution vulnerability in GitBucket 4.23.1. The flaw chains weak secret token generation, insecure plugin upload handling, and an exposed exploit endpoint to grant attackers full command execution. Attackers brute-force the Blowfish encryption key used to protect session data, upload a malicious JAR plugin through the git-lfs endpoint, and trigger code execution through a debug-style endpoint that remains reachable without authentication. The vulnerability is classified under CWE-306: Missing Authentication for Critical Function.

Critical Impact
Unauthenticated attackers can achieve arbitrary command execution on the GitBucket host, exposing source code, credentials, and adjacent infrastructure.

Affected Products

GitBucket 4.23.1
Self-hosted GitBucket deployments exposing the web interface
Instances reachable over HTTP/HTTPS without network restrictions

Discovery Timeline

2026-05-17 - CVE-2018-25332 published to NVD
2026-05-18 - Last updated in NVD database

Technical Details for CVE-2018-25332

Vulnerability Analysis

The vulnerability stems from three compounding weaknesses in GitBucket 4.23.1. First, the application generates secret tokens with insufficient entropy, allowing attackers to brute-force the Blowfish key used to protect session and signed values. Second, the git-lfs upload handler accepts arbitrary files without validating type or destination, enabling attackers to drop a JAR file into the plugin directory. Third, an exploit-style endpoint remains exposed without authentication, executing system commands when reached.

GitBucket's plugin loader processes JARs from a known location, so a forged plugin executes immediately after upload. The chained primitives convert a remote, unauthenticated HTTP request into arbitrary command execution under the user account running GitBucket.

Root Cause

The root cause is missing authentication for critical functionality combined with weak cryptographic key generation. The Blowfish key derivation uses predictable input, breaking the confidentiality and integrity properties of any data signed or encrypted with it. The plugin upload path trusts client-supplied filenames and content, and the exploit endpoint has no access control.

Attack Vector

An attacker reaches the GitBucket instance over the network. The attacker recovers the Blowfish secret through brute force, forges signed values needed to access the git-lfs endpoint, uploads a JAR plugin containing malicious Java bytecode, and invokes the exposed exploit endpoint to run operating system commands. No credentials, prior access, or user interaction is required. Technical details and a verified proof of concept are published as Exploit-DB #44668 and the VulnCheck GitBucket Advisory.

Detection Methods for CVE-2018-25332

Indicators of Compromise

Unexpected JAR files written to the GitBucket plugin directory under the application's data path.
HTTP requests to git-lfs upload endpoints from unauthenticated sources, especially with non-LFS payloads.
Requests reaching exploit or debug endpoints that should not be exposed in production builds.
Child processes spawned by the JVM running GitBucket, such as shells, curl, or wget.

Detection Strategies

Inspect web server and reverse proxy logs for POST requests to git-lfs paths followed by access to exploit endpoints from the same source.
Monitor the GitBucket plugin directory for new or modified .jar files outside of administrative change windows.
Alert on outbound network connections initiated by the GitBucket process to unfamiliar hosts.

Monitoring Recommendations

Forward GitBucket access logs and host process telemetry to a centralized analytics platform for correlation.
Baseline normal GitBucket child-process activity and alert on deviations such as /bin/sh or cmd.exe execution.
Track filesystem changes under the GitBucket home directory with integrity monitoring.

How to Mitigate CVE-2018-25332

Immediate Actions Required

Upgrade GitBucket to a release later than 4.23.1 that addresses the token, upload, and exposed endpoint issues.
Restrict network access to GitBucket using firewalls or reverse proxy allow-lists until the upgrade is complete.
Audit the plugin directory and remove any JAR files that were not installed by administrators.
Rotate any credentials, tokens, or SSH keys stored in or accessible from the GitBucket host.

Patch Information

Upgrade to a fixed GitBucket release published by the maintainers. Review the GitHub GitBucket Repository for current release notes and security advisories. Additional analysis is available in the VulnCheck GitBucket Advisory and the Szurek Security Blog.

Workarounds

Place GitBucket behind an authenticating reverse proxy that blocks anonymous access to upload and exploit endpoints.
Run the GitBucket JVM as a low-privilege user with restricted filesystem and network permissions.
Disable or remove the exposed exploit endpoint in deployments where source modification is feasible.

bash

# Configuration example: restrict GitBucket to localhost and front with authenticated proxy
java -jar gitbucket.war --host=127.0.0.1 --port=8080

# Example nginx snippet enforcing authentication before reaching GitBucket
# location / {
#     auth_basic "GitBucket";
#     auth_basic_user_file /etc/nginx/.htpasswd;
#     proxy_pass http://127.0.0.1:8080;
# }