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fix: harden XML parser against XXE in Cloud Functions sample #10236

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Merged
NimJay merged 2 commits into from
Feb 27, 2026
+17 −2
Merged

fix: harden XML parser against XXE in Cloud Functions sample #10236

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fix: harden XML parser against XXE in Cloud Functions sample
anto-1 Feb 22, 2026
9a96bbb
address review: add defense-in-depth features, make field final, fix …
anto-1 Feb 22, 2026
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12 changes: 11 additions & 1 deletion functions/http/parse-xml/src/main/java/functions/ParseXml.java
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,17 @@
import org.xml.sax.SAXException;

public class ParseXml implements HttpFunction {
private static DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
private static DocumentBuilderFactory dbFactory;

static {
dbFactory = DocumentBuilderFactory.newInstance();
try {
// Prevent XXE attacks (see https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.html)
dbFactory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);
} catch (ParserConfigurationException e) {
throw new RuntimeException(e);
}
}
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@gemini-code-assist gemini-code-assist Bot Feb 22, 2026

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security-medium medium

To improve the robustness and maintainability of the XML parser configuration, consider making the dbFactory field final and adding additional defense-in-depth features as recommended by the OWASP XXE Prevention Cheat Sheet. While disallow-doctype-decl is highly effective, these extra settings provide layered security against various XXE vectors.

  private static final DocumentBuilderFactory dbFactory;

  static {
    dbFactory = DocumentBuilderFactory.newInstance();
    try {
      // Prevent XXE attacks (see https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.html)
      dbFactory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);
      dbFactory.setFeature("http://xml.org/sax/features/external-general-entities", false);
      dbFactory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
      dbFactory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
      dbFactory.setXIncludeAware(false);
      dbFactory.setExpandEntityReferences(false);
    } catch (ParserConfigurationException e) {
      throw new RuntimeException(e);
    }
  }


// Parses a HTTP request in XML format
// (Responds with a 400 error if the HTTP request isn't valid XML.)
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