CVE-2026-31248: High severity Docling Docling METS GBS backend vulnerability
Docling's METS GBS backend is vulnerable to XML Entity Expansion (XXE) attacks thru 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.
Affected Software
Event History
Frequently Asked Questions
Which deployments are exposed?
Exposure is limited to Docling deployments that use the METS GBS backend to extract and validate XML files from .tar.gz archives. The provided information does not establish whether this backend is enabled or used by default.
What does an attacker need to exploit this issue?
An attacker needs to cause the METS GBS backend to process a crafted .tar.gz archive containing XML with nested entity definitions. The CVSS vector indicates no privileges or user interaction are required.
How can I determine whether my installation is affected?
Check whether the deployment uses the Docling METS GBS backend and accepts or processes .tar.gz archives containing XML. Versions through 2.61.0 are identified as vulnerable.