Path Traversal in Docling Document Processing Library

Executive Summary

The vulnerability in CVE-2026-44018 affects the METS-GBS backend of the Docling library versions from 2.45.0 up to but not including 2.91.0. It involves unsafe XML parsing and input document format detection that lack proper security controls.

An attacker can craft malicious METS-GBS archives that exploit XML External Entity (XXE) attacks to read sensitive local files or cause denial of service. Additionally, specially crafted archives can exhaust system resources through decompression bombs (zip bombs) or unbounded archive extraction, leading to application crashes or resource exhaustion.

This vulnerability was fixed in version 2.91.0 by introducing secure XML parsing with disabled entity resolution, DTD loading, and network access, as well as configurable limits on extraction size, file size, member count, and cumulative size tracking.

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Detection Guidance

This vulnerability affects the METS-GBS backend in Docling versions from 2.45.0 up to but not including 2.91.0, involving unsafe XML parsing and archive extraction.

Detection can involve identifying usage of vulnerable Docling versions and monitoring for processing of METS-GBS archives that could trigger XML External Entity (XXE) attacks or decompression bombs.

As the attack vector is local and requires user interaction, commands to check the installed Docling version can help detect vulnerability presence, for example:

• docling --version

Additionally, monitoring system logs for application crashes or resource exhaustion during METS-GBS archive processing may indicate exploitation attempts.

Since the vulnerability involves XML parsing, tools that scan XML files for external entity declarations (e.g., searching for "<!ENTITY" or "<!DOCTYPE") in METS-GBS archives could help detect malicious inputs.

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Impact Analysis

This vulnerability can impact you by allowing an attacker to read sensitive files on your system if you process malicious METS-GBS archives.

It can also cause denial of service by exhausting system resources such as memory and disk space, potentially crashing the application or making it unavailable.

The attack requires local access, low complexity, no privileges, but does require user interaction.

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Compliance Impact

The vulnerability in Docling's METS-GBS backend allows attackers to read sensitive files and cause denial of service through resource exhaustion or crashes. This could potentially lead to unauthorized access to sensitive data or disruption of services.

Such impacts may affect compliance with standards and regulations like GDPR or HIPAA, which require protection of sensitive data and system availability. However, the provided information does not explicitly state the compliance implications or specific regulatory impacts.

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Mitigation Strategies

The primary mitigation is to upgrade Docling to version 2.91.0 or later, where the vulnerability is fixed.

Version 2.91.0 introduces secure XML parsing by disabling entity resolution, DTD loading, and network access, and enforces configurable limits on archive extraction size and member count.

If upgrading immediately is not possible, avoid processing METS-GBS archives from untrusted sources.

Alternatively, pre-validate METS-GBS archives in an isolated environment with resource limits to prevent resource exhaustion or crashes.

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