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CVE-2026-55240

CRITICAL 9.1

Published 2026-10-15 · Last modified 2026-10-15

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.

ELEVATED IMPACT

Severe if exploited (CVSS 9.1), but no known exploitation and low modeled probability. Patch on a normal cadence.

Exploitation likelihood

0.6%chance of exploitation in 30 days · 47th percentile

○ In CISA KEV ○ Catalogued PoC

Impact if exploited

9.1CVSS 3.1 · CRITICAL

  • ConfidentialityHigh
  • IntegrityHigh
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ⚠Privileges: Requires an admin / high-privilege account
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

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Data snapshot:

Affected

Vendors Msgbyte

Products Tianji

Weakness (CWE)

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

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

References and research data (JSON)

All CVSS metrics

  • CRITICAL 9.1 v3.1 · CNA Primary
    CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
  • CRITICAL 9.1 v3.1 · NVD Secondary
    CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

References

Advisories

Technical & other

Sources: NVD · CVE.org · EPSS