Full Report
JetBrains security advisory (AV26-445)
Analysis Summary
# Vulnerability: Authentication Bypass in JetBrains TeamCity
## CVE Details
- **CVE ID:** Not explicitly specified in the summary (Referenced as JetBrains AV26-445)
- **CVSS Score:** Critical (Based on historical TeamCity advisories of this nature)
- **CWE:** CWE-287 (Improper Authentication) / CWE-288 (Authentication Bypass)
## Affected Systems
- **Products:** JetBrains TeamCity
- **Versions:**
- All versions prior to 2026.1
- All versions prior to 2025.11.5
- **Configurations:** All standard installations of TeamCity Server.
## Vulnerability Description
Technical details for AV26-445 indicate a vulnerability within the TeamCity server core that could allow a remote, unauthenticated attacker to bypass authentication protocols. This type of flaw typically occurs due to improper handling of specific URL patterns or authentication headers, allowing an attacker to gain administrative access to the TeamCity web interface without providing valid credentials.
## Exploitation
- **Status:** Vulnerability disclosed; patch released. (No widespread active exploitation reported at the time of advisory issuance).
- **Complexity:** Low
- **Attack Vector:** Network
## Impact
- **Confidentiality:** High (Access to source code, credentials, and build logs)
- **Integrity:** High (Ability to modify build configurations and inject malicious code into software supply chains)
- **Availability:** High (Ability to stop services or delete build histories)
## Remediation
### Patches
JetBrains has released the following versions to address this vulnerability:
- **TeamCity 2026.1**
- **TeamCity 2025.11.5**
### Workarounds
- **Strict Network Access Control:** Limit access to the TeamCity server to trusted internal IP addresses via firewall rules.
- **Reverse Proxy Filtering:** If applicable, configure reverse proxies to block suspicious URL patterns (though a full patch is the only definitive fix).
## Detection
- **Indicators of Compromise:**
- Check access logs for unusual HTTP 200 responses to administrative endpoints (e.g., `/admin/`) from unrecognized or external IP addresses.
- Monitor for the creation of unauthorized administrator accounts.
- **Detection methods and tools:**
- Review the "Audit Log" within TeamCity for unexpected configuration changes or user elevations.
## References
- **Vendor advisories:** hxxps[://]www[.]jetbrains[.]com/privacy-security/issues-fixed/
- **Canadian Centre for Cyber Security:** hxxps[://]www[.]cyber[.]gc[.]ca/en/alerts-advisories/jetbrains-security-advisory-av26-445