Atlassian has disclosed a critical security vulnerability in Bamboo Data Center and Server that could allow attackers to execute operating system commands remotely.
The flaw, tracked as CVE-2026-21571, carries a CVSS score of 9.4, indicating a high-severity risk for enterprise environments.
The vulnerability was published on April 21, 2026, as part of Atlassian’s monthly Security Bulletin, which outlines newly discovered and patched issues across its product suite.
Bamboo, a widely used Continuous Integration and Continuous Delivery (CI/CD) platform, is heavily relied upon by development teams to automate build and deployment workflows, making this flaw particularly concerning.
According to the National Vulnerability Database (NVD), the issue affects multiple Bamboo Data Center and Server versions, including 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.
Atlassian noted that the vulnerability originates from a third-party dependency, though it emphasized that its implementation reduces the overall risk. Despite this, the vulnerability remains classified as critical due to its potential impact.
Technically, the flaw is an OS command injection vulnerability that can be exploited over a network with low attack complexity.
It requires only low-level authentication and does not need user interaction. This makes it easier for attackers to exploit in real-world scenarios.
Successful exploitation allows attackers to run arbitrary commands on affected systems. This can result in severe consequences, including unauthorized access to sensitive data, manipulation of CI/CD pipelines, and disruption of system operations.
In particular, attackers could inject malicious code into automated build processes, potentially compromising software supply chains at scale.
Atlassian has released patched versions to address the issue. Organizations are advised to upgrade immediately to Bamboo Data Center 12.1.6 (LTS), 10.2.18 (LTS), or 9.6.25, depending on their current deployment.
These updates contain fixes that mitigate the vulnerability and reduce the risk of exploitation.
For organizations unable to patch immediately, Atlassian recommends reviewing its Vulnerability Disclosure Portal to assess exposure and identify appropriate mitigation steps.
Security teams should also audit their Bamboo deployments, monitor authentication logs for suspicious activity, and review CI/CD pipelines for any unauthorized changes.
CVE-2026-21571 is one of 38 vulnerabilities addressed in Atlassian’s April 2026 Security Bulletin. These include 31 high-severity and 7 critical issues across products such as Jira, Confluence, Bitbucket, and Jira Service Management.
Other notable vulnerabilities include a maximum severity CVSS 10.0 cross-site scripting flaw and a remote code execution issue linked to third-party dependencies.
Given Bamboo’s central role in software development pipelines, unpatched systems pose a serious risk to enterprise environments.
Organizations are strongly urged to apply updates promptly to prevent potential supply chain attacks and operational disruptions.
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