CVE-2026-21571: 
Bamboo Schwachstellenanalyse und -minderung

CVE-2026-21571 is a Critical severity OS Command Injection vulnerability in Atlassian Bamboo Data Center that allows authenticated remote attackers to execute arbitrary OS commands on affected systems. The vulnerability was introduced in versions 9.6.0, 10.0.0, 10.1.0, 10.2.0, 11.0.0, 11.1.0, 12.0.0, and 12.1.0 of Bamboo Data Center. It was disclosed and patched on April 21, 2026, as part of Atlassian's monthly security bulletin. The vulnerability carries a CVSS v4.0 base score of 9.4 (Critical) (Atlassian Advisory, Github Advisory).

The vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), meaning Bamboo Data Center fails to properly sanitize user-supplied input before incorporating it into OS-level commands. An authenticated attacker can exploit this over the network with low attack complexity and no special attack requirements or user interaction, making it straightforward to weaponize with valid credentials. Atlassian notes this is a vulnerability in a non-Atlassian dependency used by Bamboo Data Center, though the application's use of the dependency presents a critical assessed risk in this context (Atlassian Advisory, Github Advisory). No public proof-of-concept exploit code has been identified at this time (Github Advisory).

Successful exploitation allows an authenticated attacker to execute arbitrary OS commands on the Bamboo Data Center host, resulting in high impact to confidentiality, integrity, and availability of both the vulnerable system and subsequent systems. An attacker could exfiltrate sensitive CI/CD pipeline data, credentials, and source code; modify build configurations or artifacts; or disrupt build and deployment operations entirely. Given Bamboo's role as a CI/CD orchestration platform, compromise could facilitate lateral movement into connected development infrastructure, code repositories, and deployment targets (Atlassian Advisory, Github Advisory).

1. Reconnaissance: Identify internet-facing or network-accessible Bamboo Data Center instances running affected versions (9.6.0–9.6.24, 10.0.0–10.0.3, 10.1.0–10.1.1, 10.2.0–10.2.16, 11.0.0–11.0.8, 12.0.0–12.0.2, or 12.1.0–12.1.3) using tools such as Shodan, Censys, or internal network scanning.
2. Obtain valid credentials: Acquire low-privileged Bamboo user credentials through phishing, credential stuffing, or use of a free/trial account, as only low-level authentication is required.
3. Identify the vulnerable endpoint: Locate the application functionality or API endpoint that passes user-controlled input to an OS command without adequate sanitization (specific endpoint details are not publicly disclosed).
4. Craft malicious payload: Construct an HTTP request containing OS command injection characters (e.g., ;, &&, |, backticks) embedded in the vulnerable parameter to append or replace the intended OS command.
5. Execute arbitrary commands: Submit the crafted request to the Bamboo Data Center instance; the server executes the injected command as the Bamboo service account, enabling reverse shell establishment, credential harvesting, or further lateral movement (Atlassian Advisory, Github Advisory).

• Network: Unexpected outbound connections from the Bamboo server to external IPs or unusual internal hosts; anomalous DNS lookups originating from the Bamboo process.
• Logs: Bamboo application logs showing unusual or malformed requests containing shell metacharacters (;, &&, |, backticks) in parameter values; authentication events from unfamiliar accounts or IP addresses.
• Process: Unexpected child processes spawned by the Bamboo Java process (e.g., /bin/sh, /bin/bash, cmd.exe, curl, wget, python, nc) indicating OS command execution.
• File System: New or modified files in the Bamboo installation directory, temporary directories, or home directories of the Bamboo service account; presence of web shells, reverse shell scripts, or unauthorized SSH keys.
• Scheduled Tasks/Cron: New cron jobs or scheduled tasks created under the Bamboo service account that were not previously present.

Atlassian recommends upgrading Bamboo Data Center to the latest available version. Specific minimum fixed versions are: 9.6.25 or later for the 9.6.x LTS branch, 10.2.18 or later for the 10.2.x LTS branch, and 12.1.6 or later for the 12.1.x LTS branch. Versions in the 10.0.x, 10.1.x, 11.0.x, 11.1.x, and 12.0.x branches should be upgraded to a supported LTS fixed version. As an interim measure, restrict Bamboo Data Center access to trusted, authenticated users only and limit network exposure until patching is complete (Atlassian Advisory, Github Advisory).

The vulnerability received coverage from multiple security news outlets including SecurityOnline, CyberSecurityNews, GBHackers, Security Boulevard, and The Hacker News (in their weekly recap), highlighting the critical risk to CI/CD pipelines (SecurityOnline, The Hacker News). Community commentary emphasized the elevated risk posed by command injection in CI/CD infrastructure, given the potential for supply chain compromise. Atlassian issued the patch as part of its April 21, 2026 monthly security bulletin, which also addressed 31 high-severity and 6 other critical-severity vulnerabilities across its product suite (Atlassian Advisory).