CVE intelligence and bounded remediation

CVE-2025-53890 — pyload is an open-source Download Manager written in pure Python

Critical CVSS 9.8

pyload is an open-source Download Manager written in pure Python. An unsafe JavaScript evaluation vulnerability in pyLoad’s CAPTCHA processing code allows unauthenticated remote attackers to execute arbitrary code in the client browser and potentially the backend server. Exploitation requires no user interaction or authentication and can result in session hijacking, credential theft, and full system remote code execution. Commit 909e5c97885237530d1264cfceb5555870eb9546, the patch for the issue, is included in version 0.5.0b3.dev89.

Severity
Critical
CVSS
9.8 (3.1)
Published
2025-07-15
CISA KEV
Not currently listed
Ecosystem
javascript/npm
Weaknesses
CWE-94

Affected products

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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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