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Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')

CVE-2026-31248

High
7.5/10

Summary

Docling's METS GBS backend is vulnerable to XML Entity Expansion (XXE) attacks through 2.61.0. The backend extracts and validates XML files from .tar.gz archives using etree.fromstring() without disabling entity resolution. An attacker can craft a malicious XML file with nested entity definitions (XML Bomb) and package it into a .tar.gz archive. When processed by Docling, the exponential expansion of entities during XML parsing leads to excessive resource consumption, resulting in a denial of service (DoS) condition on the system running the Docling parser.

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

CWE-776 - Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')

The software uses XML documents and allows their structure to be defined with a Document Type Definition (DTD), but it does not properly control the number of recursive definitions of entities.

References

Advisory Timeline

  • Published