CVE intelligence and bounded remediation

CVE-2019-18839 — FUDForum 3.0.9 is vulnerable to Stored XSS via the nlogin parameter

Critical CVSS 9

FUDForum 3.0.9 is vulnerable to Stored XSS via the nlogin parameter. This may result in remote code execution. An attacker can use a user account to fully compromise the system using a POST request. When the admin visits the user information, the payload will execute. This will allow for PHP files to be written to the web root, and for code to execute on the remote server.

Severity
Critical
CVSS
9 (3.1)
Published
2019-11-13
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-78, CWE-79

Affected products

  • fudforum / fudforum / 3.0.9

Matched remediation archetype

Command, code, expression, and template injection

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Check exposure

  • Trace untrusted values to process execution, interpreters, evaluators, template engines, dynamic imports, and administrative scripting features.
  • Determine whether the affected path is reachable across each trust boundary and which service account or host privilege it inherits.
  • Review configuration for optional execution features, unsafe compatibility modes, and shell invocation.

Remediate safely

  • Replace string-built commands or evaluated code with fixed operations and structured argument APIs that do not invoke a shell.
  • Use strict allowlists for operation identifiers and reject unexpected input before it reaches any interpreter.
  • Update the affected component and add inert regression tests covering metacharacters, encoding variants, and alternate request paths.

Authoritative sources

Complete CVE record and remediation plan

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