CVE-2026-20104

#!/usr/bin/env python3 # PoC Concept for CVE-2026-20104 # Requires physical access or Level-15 privileges to the device. import os def exploit_bootloader_bypass(): # Identify target package configuration or binary on the flash target_path = "/flash/packages.conf" print(f"[*] Targeting {target_path}...") # Simulate manipulation of the binary to bypass integrity checks # In a real scenario, this involves mounting the partition and hex editing try: with open(target_path, "r+b") as f: # Example: Injecting a payload or modifying headers to bypass signature verification # This is pseudo-code representing the 'manipulating loaded binaries' step print("[+] Modifying binary to bypass integrity checks...") # f.write(malicious_payload) pass except IOError: print("[-] Error accessing file system. Check privileges.") return print("[+] Binary manipulation complete.") print("[*] Rebooting device to trigger execution of arbitrary code...") # Trigger reboot to exploit the vulnerability during boot time # os.system("reboot") if __name__ == "__main__": print("CVE-2026-20104 PoC - Cisco IOS XE Bootloader Bypass") exploit_bootloader_bypass()

{"cve": {"id": "CVE-2026-20104", "sourceIdentifier": "[email protected]", "published": "2026-03-25T16:16:14.143", "lastModified": "2026-03-26T15:13:15.790", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "A vulnerability in the bootloader of Cisco IOS XE Software for Cisco Catalyst 9200 Series Switches, Cisco Catalyst ESS9300 Embedded Series Switches, Cisco Catalyst IE9310 and IE9320 Rugged Series Switches, and Cisco IE3500 and IE3505 Rugged Series Switches could allow an authenticated, local attacker with level-15 privileges or an unauthenticated attacker with physical access to an affected device to execute arbitrary code at boot time and break the chain of trust.\r\n\r This vulnerability is due to insufficient validation of software at boot time. An attacker could exploit this vulnerability by manipulating the loaded binaries on an affected device to bypass some of the integrity checks that are performed during the boot process. A successful exploit could allow the attacker to execute code that bypasses the requirement to run Cisco-signed images.\r\n\r Cisco has assigned this security advisory a Security Impact Rating (SIR) of High rather than Medium as the score indicates because this vulnerability allows an attacker to bypass a major security feature of a device."}, {"lang": "es", "value": "Una vulnerabilidad en el bootloader del software Cisco IOS XE para los switches Cisco Catalyst serie 9200, los switches integrados Cisco Catalyst ESS9300, los switches robustos Cisco Catalyst IE9310 e IE9320, y los switches robustos Cisco IE3500 e IE3505 podría permitir a un atacante local autenticado con privilegios de nivel 15 o a un atacante no autenticado con acceso físico a un dispositivo afectado ejecutar código arbitrario en el momento del arranque y romper la cadena de confianza.\nEsta vulnerabilidad se debe a una validación insuficiente del software en el momento del arranque. Un atacante podría explotar esta vulnerabilidad manipulando los binarios cargados en un dispositivo afectado para eludir algunas de las comprobaciones de integridad que se realizan durante el proceso de arranque. Un exploit exitoso podría permitir al atacante ejecutar código que elude el requisito de ejecutar imágenes firmadas por Cisco.\nCisco ha asignado a este aviso de seguridad una Calificación de Impacto de Seguridad (SIR) de Alta en lugar de Media, como indica la puntuación, porque esta vulnerabilidad permite a un atacante eludir una característica de seguridad importante de un dispositivo."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N", "baseScore": 6.1, "baseSeverity": "MEDIUM", "attackVector": "PHYSICAL", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 0.9, "impactScore": 5.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-124"}]}], "references": [{"url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-xe-secureboot-bypass-B6uYxYSZ", "source": "[email protected]"}]}}