PatchSiren cyber security CVE debrief
CVE-2026-29514 netbox-community CVE debrief
A remote code execution vulnerability exists in NetBox versions 4.3.5 through 4.5.4. The RenderTemplateMixin.get_environment_params() method allows authenticated users with exporttemplate or configtemplate permissions to execute arbitrary code by specifying malicious Python callables in the environment_params field. Attackers can bypass Jinja2 SandboxedEnvironment protections by setting the finalize parameter to an importable Python callable such as subprocess.getoutput, which is invoked on every rendered expression outside the sandbox's call interception mechanism. This achieves remote code execution as the NetBox service user. The vulnerability was disclosed on 2026-05-04 and last modified on 2026-05-21. A fix is available in version 4.6.1.
- Vendor
- netbox-community
- Product
- netbox
- CVSS
- HIGH 8.7
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-05-04
- Original CVE updated
- 2026-05-21
- Advisory published
- 2026-05-04
- Advisory updated
- 2026-05-21
Who should care
Organizations running NetBox versions 4.3.5 through 4.5.4, particularly those with multiple users granted exporttemplate or configtemplate permissions. Security teams responsible for network infrastructure management platforms and NetBox administrators should prioritize patching.
Technical summary
The vulnerability resides in NetBox's RenderTemplateMixin class, specifically the get_environment_params() method. This method constructs Jinja2 environment parameters from user-supplied configuration without adequate validation. Attackers with exporttemplate or configtemplate permissions can manipulate the environment_params field to inject malicious Python callables. The attack leverages the finalize parameter, which Jinja2 invokes on every expression result during template rendering. Because finalize operates outside the SandboxedEnvironment's call interception mechanism, attackers can execute arbitrary system commands as the NetBox service user. The vulnerability bypasses intended sandbox protections by exploiting legitimate Jinja2 functionality in an unintended manner.
Defensive priority
HIGH
Recommended defensive actions
- Upgrade NetBox to version 4.6.1 or later to remediate this vulnerability
- Review and audit user accounts with exporttemplate or configtemplate permissions for unauthorized activity
- Implement principle of least privilege by restricting exporttemplate and configtemplate permissions to only necessary administrative accounts
- Monitor NetBox service account activity for unusual process execution or network connections
- If immediate patching is not possible, consider disabling export template and config template functionality until the patch can be applied
- Review application logs for suspicious environment_params configurations containing finalize or other callable references
Evidence notes
The vulnerability affects NetBox versions 4.3.5 through 4.5.4. The root cause is improper validation of the environment_params field in RenderTemplateMixin.get_environment_params(), which allows attackers to inject arbitrary Python callables that bypass Jinja2 sandbox protections. The finalize parameter is particularly dangerous as it is called on every rendered expression. The fix was committed in d124c5fe86e12aad61285133c0caf16adcda8f2e and released in version 4.6.1.
Official resources
2026-05-04