CVE intelligence and bounded remediation

CVE-2025-65289 — Mercurycom Mr816 Firmware security vulnerability

Medium CVSS 6.1

A stored Cross site scripting (XSS) vulnerability in the Mercury MR816v2 (081C3114 4.8.7 Build 110427 Rel 36550n) router allows a remote attacker on the LAN to inject JavaScript into the router's management UI by submitting a malicious hostname. The injected script is stored and later executed in the context of an administrator's browser (for example after DHCP release/renew triggers the interface to display the stored hostname). Because the management interface uses weak/basic authentication and does not properly protect or isolate session material, the XSS can be used to exfiltrate the admin session and perform administrative actions.

Severity
Medium
CVSS
6.1 (3.1)
Published
2025-12-09
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-79

Affected products

  • mercurycom / mr816_firmware / 081c3114_4.8.7

Matched remediation archetype

Cross-site scripting and unsafe browser output

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Check exposure

  • Trace reflected, stored, and DOM-derived untrusted values into HTML, attributes, URLs, styles, scripts, and client-side template sinks.
  • Identify affected origins, authenticated user roles, sensitive browser capabilities, and where content is shared across tenants.
  • Review framework escaping, rich-text sanitization, legacy templates, and client-side rendering paths.

Remediate safely

  • Use context-aware framework output encoding and safe DOM APIs; keep untrusted data out of executable contexts.
  • Sanitize intentionally supported markup with a maintained allowlist policy and validate URLs and attributes separately.
  • Update affected rendering components and add tests for every output context using inert sentinel markup.

Authoritative sources

Complete CVE record and remediation plan

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