CVE-2021-41178

Nextcloud is an open-source, self-hosted productivity platform. Prior to versions 20.0.13, 21.0.5, and 22.2.0, a file traversal vulnerability makes an attacker able to download arbitrary SVG images from the host system, including user provided files. This could also be leveraged into a XSS/phishing attack, an attacker could upload a malicious SVG file that mimics the Nextcloud login form and send a specially crafted link to victims. The XSS risk here is mitigated due to the fact that Nextcloud employs a strict Content-Security-Policy disallowing execution of arbitrary JavaScript. It is recommended that the Nextcloud Server be upgraded to 20.0.13, 21.0.5 or 22.2.0. There are no known workarounds aside from upgrading.

Nextcloud is an open-source, self-hosted productivity platform. Prior to versions 20.0.13, 21.0.5, and 22.2.0, a file traversal vulnerability makes an attacker able to download arbitrary SVG images from the host system, including user provided files. This could also be leveraged into a XSS/phishing attack, an attacker could upload a malicious SVG file that mimics the Nextcloud login form and send a specially crafted link to victims. The XSS risk here is mitigated due to the fact that Nextcloud employs a strict Content-Security-Policy disallowing execution of arbitrary JavaScript. It is recommended that the Nextcloud Server be upgraded to 20.0.13, 21.0.5 or 22.2.0. There are no known workarounds aside from upgrading.

Nextcloud es una plataforma de productividad de código abierto y auto-alojada. Antes de las versiones 20.0.13, 21.0.5 y 22.2.0, una vulnerabilidad de salto de archivos hace que un atacante pueda descargar imágenes SVG arbitrarias del sistema anfitrión, incluyendo archivos proporcionados por el usuario. Esto también podría ser aprovechado en un ataque de tipo XSS/phishing, un atacante podría subir un archivo SVG malicioso que imita el formulario de inicio de sesión de Nextcloud y enviar un enlace especialmente diseñado a las víctimas. El riesgo de un ataque de tipo XSS en este caso está mitigado debido a que Nextcloud emplea una estricta Política de Seguridad de Contenidos que no permite la ejecución de JavaScript arbitrario. Es recomendado actualizar el servidor Nextcloud a la versión 20.0.13, 21.0.5 o 22.2.0. No se presentan soluciones conocidas aparte de la actualización