Skip to main content

Improper Restriction of XML External Entity Reference

CVE-2019-12331

High
8.8/10

Summary

PHPOffice PhpSpreadsheet before 1.8.0 has an XXE issue. The XmlScanner decodes the sheet1.xml from an .xlsx to utf-8 if something else than UTF-8 is declared in the header. This was a security measurement to prevent CVE-2018-19277 but the fix is not sufficient. By double-encoding the the xml payload to utf-7 it is possible to bypass the check for the string ,<!ENTITY' and thus allowing for an xml external entity processing (XXE) attack.

  • LOW
  • NETWORK
  • HIGH
  • UNCHANGED
  • REQUIRED
  • NONE
  • HIGH
  • HIGH

CWE-611 - Improper Restriction of XML External Entity Reference

Listed 4th in the 'OWASP Top Ten', XML External Entities (XXE) vulnerability allows attackers to provide an XML input that contains an external entity. When the XML is parsed, it can cause data extraction and manipulation, execution of commands, denial-of-service attacks, and server-side request forgery.

References

Advisory Timeline

  • Published