CVE-2026-55240 Tianji: Remote Code Execution via lodash template evaluate pattern in survey feed templates
A workspace administrator can inject JavaScript into survey templates, leading to remote code execution when unauthenticated users submit responses.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-55240?
CVE-2026-55240 is a critical code injection vulnerability in msgbyte tianji, published on 15 Oct 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
Tianji is an open source analytics, uptime monitoring, and server status platform. Prior to 1.31.29, formatString() in src/server/utils/template.ts passes survey feedTemplate and monitor notification templates to lodash template(), while the default evaluate pattern remains enabled. A workspace administrator can store an evaluate block using the <% code %> form, and the public survey.submit endpoint renders a survey template when an unauthenticated user submits a response. The compiled template executes server-side JavaScript in the Tianji Node.js process, allowing command execution, secret disclosure, data modification, or service disruption. This issue is fixed in version 1.31.29.
Weakness: CWE-1336
Which versions are affected by CVE-2026-55240?
How do I fix CVE-2026-55240?
No fix has been published for CVE-2026-55240 yet. Limit exposure of the affected software until one is available.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2026-55240 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55240 exists.
Sources
Also known as GHSA-5grg-j3cr-3hpm.