NetBox RCE via Jinja2 Template Injection (CVE-2026-29514)

NetBox, a widely-used infrastructure resource modeling application, is vulnerable to remote code execution (RCE) in versions 4.3.5 through 4.5.4. This vulnerability, identified as CVE-2026-29514, resides in the RenderTemplateMixin.get_environment_params() method. An authenticated attacker with exporttemplate or configtemplate permissions can exploit this flaw by injecting malicious Python callables into the environment_params field. Successful exploitation allows the attacker to bypass the Jinja2 SandboxedEnvironment, achieving arbitrary code execution as the NetBox service user. This RCE can lead to complete system compromise, data exfiltration, or denial of service. Defenders should prioritize patching and implement the detection measures outlined below.

Attack Chain

1. An authenticated user logs into the NetBox web application with exporttemplate or configtemplate permissions.
2. The attacker crafts a malicious request to modify or create an export/config template.
3. Within the request, the attacker injects a Python callable, such as subprocess.getoutput, into the environment_params field. The finalize parameter of the Jinja2 environment is set to this callable.
4. NetBox processes the request, and the Jinja2 environment is initialized with the attacker-controlled finalize parameter.
5. When the template is rendered, every expression outside the sandbox’s call interception mechanism is processed.
6. The injected callable (subprocess.getoutput) is invoked on the rendered expression.
7. The subprocess.getoutput callable executes arbitrary shell commands as the NetBox service user.
8. The attacker gains remote code execution, potentially leading to full system compromise or data exfiltration.

Impact

Successful exploitation of CVE-2026-29514 allows an authenticated attacker to execute arbitrary code on the NetBox server. The impact includes potential full system compromise, data exfiltration, and denial of service. Given that NetBox is often used to manage critical infrastructure information, a successful attack could have significant consequences, potentially affecting numerous organizations that rely on accurate network data.

Recommendation

• Upgrade NetBox to a patched version (4.5.5 or later) to remediate CVE-2026-29514.
• Implement the provided Sigma rule to detect attempts to inject malicious callables into environment_params via webserver logs.
• Review and restrict exporttemplate and configtemplate permissions to only those users who require them.