CVE-2026-31248: Docling Docling's METS GBS Backend Is Vulnerability

HIGH
Advisory Identifier: GHSA-9f4q-q82q-4359
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CVSS 7.5
CWE-776
Published
Advisory Summary

CVE-2026-31248 is a HIGH (CVSS 7.5) docling's mets gbs backend is vulnerability (CWE-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')) affecting Docling libraries in the PyPI ecosystem. The issue involves docling's mets gbs backend is vulnerable to xml entity expansion (xxe) attacks. Remediation is available in the latest vendor maintenance releases.

CVE-2026-31248 at a Glance

CVE Identifier CVE-2026-31248
GHSA Identifier GHSA-9f4q-q82q-4359
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
Affected Product Docling
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-31248

To remediate this vulnerability, upgrade all affected Docling dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

docling fixed: Latest secure release 
pip install docling>=Latest secure release
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show docling

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-31248, inspect your installed packages using pip:

pip show docling

Analyze the terminal output to locate any version of Docling in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The pip show docling command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion'), where the product 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. In Docling, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

CVE-2026-31248 Affected Docling Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
docling
pypi/docling
PyPI
≤ 2.61.0

References

NVD — CVE-2026-31248 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-31248
Docling Source Repository REPOSITORY
https://github.com/docling-project/docling
www.notion.so/cve-2026-31248-35d1... WEB
https://www.notion.so/CVE-2026-31248-35d1e1393188818585b2ce3b9ce24686

Frequently Asked Questions

What is CVE-2026-31248?
CVE-2026-31248 is a security vulnerability in Docling involving Docling's METS GBS backend is vulnerable to XML Entity Expansion (XXE) attacks under CWE-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion').
Which Docling versions are affected?
Affected versions include releases prior to current release patches across affected packages: docling.
What version fixes CVE-2026-31248?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is docling affected?
Yes, docling is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2026-31248?
CVE-2026-31248 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-31248?
CVE-2026-31248 is classified under CWE-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion') (The product 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.).
How can I check PyPI dependencies for CVE-2026-31248?
Run the dependency tree command: 'pip show docling'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9f4q-q82q-4359",
  "modified" : "2026-05-18T15:21:03Z",
  "published" : "2026-05-11T18:31:44Z",
  "aliases" : [ "CVE-2026-31248" ],
  "summary" : "Docling's METS GBS backend is vulnerable to XML Entity Expansion (XXE) attacks",
  "details" : "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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "docling"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "2.61.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-31248"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/docling-project/docling"
  }, {
    "type" : "WEB",
    "url" : "https://www.notion.so/CVE-2026-31248-35d1e1393188818585b2ce3b9ce24686"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-776" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-18T15:21:03Z",
    "nvd_published_at" : "2026-05-11T17:16:19Z"
  }
}