CVE-2021-36159

libfetch versiones anteriores al 26-07-2021, como se usa en apk-tools, xbps, y otros productos, maneja inapropiadamente las cadenas numéricas para los protocolos FTP y HTTP. La implementación del modo pasivo de FTP permite una lectura fuera de límites porque strtol se usa para analizar los números relevantes en bytes de dirección. No comprueba si la línea termina prematuramente. Si lo hace, la condición para bucle comprueba el terminador "\0" un byte demasiado tarde

The passive mode in FTP communication allows an out of boundary read while libfetch uses strtol to parse the relevant numbers into address bytes. It does not check if the line ends prematurely. If it does, the for-loop condition checks for *p == '\0' one byte too late because p++ was already performed. The connection buffer size can be controlled by a malicious FTP server because the size is increased until a newline is encountered (or no more characters are read). This also allows to move the buffer into more interesting areas within the address space, potentially parsing relevant numbers for the attacker. Since these bytes become available to the server in form of a new TCP connection to a constructed port number or even part of the IPv6 address this is a potential information leak.