CVE-2025-59456 Overview
CVE-2025-59456 is a path traversal vulnerability in JetBrains TeamCity versions prior to 2025.07.2. The flaw resides in the project archive upload functionality, where insufficient validation of archive entry paths allows an authenticated attacker with high privileges to write files outside the intended extraction directory. Successful exploitation can compromise file integrity on the TeamCity server and disrupt continuous integration workflows. JetBrains addressed the issue in TeamCity 2025.07.2. The vulnerability is tracked under CWE-23: Relative Path Traversal.
Critical Impact
Authenticated attackers can write arbitrary files on the TeamCity server through crafted project archive uploads, threatening build integrity and server stability.
Affected Products
- JetBrains TeamCity versions prior to 2025.07.2
- Self-hosted TeamCity build server deployments
- CI/CD pipelines relying on project archive import functionality
Discovery Timeline
- 2025-09-17 - CVE-2025-59456 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-59456
Vulnerability Analysis
CVE-2025-59456 is a relative path traversal weakness [CWE-23] triggered during the extraction of user-supplied project archives in JetBrains TeamCity. When an administrator or privileged user uploads a project archive, TeamCity extracts its contents onto the server file system. The extraction routine fails to properly canonicalize or validate entry paths within the archive. An attacker who controls the archive contents can embed entries containing traversal sequences such as ../ to escape the destination directory. The result is arbitrary file write to locations outside the intended project directory. Because TeamCity stores build configurations, plugins, and server data on disk, writing to unexpected paths can overwrite configuration files, plant malicious scripts in build agent working directories, or corrupt server state. Although the flaw requires high privileges to exploit, TeamCity administrators frequently hold trust boundaries across multiple projects and pipelines, making misuse impactful.
Root Cause
The root cause is insufficient validation of file entry names during archive extraction. The upload handler trusts the archive's internal path structure and does not verify that the resolved destination path remains within the target extraction directory. This is a classic Zip Slip pattern common to archive processing routines that omit canonical path comparison before writing entries to disk.
Attack Vector
Exploitation requires network access to the TeamCity web interface and authenticated access with high privileges, typically a system administrator role capable of importing or restoring project archives. The attacker crafts an archive containing entries with traversal sequences, uploads it through the project archive upload endpoint, and the server writes those entries to attacker-chosen paths. No user interaction beyond the attacker's own upload action is required.
No verified proof-of-concept code is publicly available. See the JetBrains Security Issues Fixed advisory for vendor-supplied technical context.
Detection Methods for CVE-2025-59456
Indicators of Compromise
- Unexpected files appearing outside the TeamCity project data directory following an archive upload event
- Project archive upload requests originating from administrator accounts at unusual times or from unfamiliar source IP addresses
- Modified TeamCity configuration files, plugin directories, or startup scripts with timestamps aligned to archive import activity
Detection Strategies
- Audit TeamCity server logs for POST requests to project import and archive upload endpoints, correlating with subsequent file system writes
- Inspect uploaded archive contents for entries containing ../, ..\, or absolute path prefixes before allowing extraction
- Monitor file integrity on TeamCity installation directories, plugin folders, and build agent working paths
Monitoring Recommendations
- Enable and centralize TeamCity audit logs to capture project configuration import actions and the user identities behind them
- Alert on file creation or modification events under TeamCity system directories initiated by the TeamCity service account outside standard build operations
- Track privileged account activity, including creation of new administrator accounts and use of archive upload features
How to Mitigate CVE-2025-59456
Immediate Actions Required
- Upgrade JetBrains TeamCity to version 2025.07.2 or later without delay
- Review recent project archive upload history and validate the integrity of TeamCity server files
- Rotate credentials, API tokens, and secrets stored on the TeamCity server if unauthorized archive uploads are suspected
Patch Information
JetBrains released the fix in TeamCity 2025.07.2. Refer to the JetBrains Security Issues Fixed page for the official advisory and download links. Apply the update to all self-hosted TeamCity servers and verify the version banner after upgrade.
Workarounds
- Restrict administrator role assignments to a minimal set of trusted personnel until patching is complete
- Disable or restrict the project archive import feature through role-based permissions where operationally feasible
- Place the TeamCity web interface behind a VPN or IP allowlist to reduce exposure of privileged endpoints
# Verify TeamCity server version after upgrade
curl -s -u <admin_user>:<admin_token> \
https://teamcity.example.com/app/rest/server \
| grep -oE 'version="[^"]+"'
# Expected output should reflect 2025.07.2 or later
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
