What is CVE-2026-55240?

CVE-2026-55240 is a critical-severity vulnerability, classified under Improper Neutralization of Special Elements Used in a Template Engine. CVSS score: 9.1/10. Published 2026-10-15.

How severe is CVE-2026-55240?

Critical severity. CVSS v3 base score is 9.1 out of 10.

CVE-2026-55240

CVE-2026-55240

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.

Published 2026-10-15.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Weakness classification (CWE)

CWE-1336 — Improper Neutralization of Special Elements Used in a Template Engine

References

Frequently asked questions

What is CVE-2026-55240?: CVE-2026-55240 is a critical-severity vulnerability, classified under Improper Neutralization of Special Elements Used in a Template Engine. CVSS score: 9.1/10. Published 2026-10-15.
How severe is CVE-2026-55240?: Critical severity. CVSS v3 base score is 9.1 out of 10.