CVE-2015-9542: 
Linux Debian vulnerability analysis and mitigation

CVE-2015-9542 affects the pam_radius authentication module version 1.4.0 and earlier. The vulnerability was discovered in the add_password function within pam_radius_auth.c, where incorrect password length checking could lead to security issues. The vulnerability was publicly disclosed and patched in February 2020 (NVD, Ubuntu Notice).

The vulnerability stems from improper password length validation in the add_password() function of pam_radius_auth.c. Specifically, the function performed an incorrect memcpy operation using strlen(password) instead of the properly bounded length variable, leading to a potential stack-based buffer overflow (FreeRADIUS Commit).

The vulnerability could allow an attacker to cause a denial of service (DoS) by crashing applications using the PAM stack for authentication. While arbitrary code execution might be theoretically possible, this depends on various factors including the application, C library, and compiler settings (Debian LTS).

The vulnerability was fixed in multiple distributions through security updates: Ubuntu released fixes for versions 19.10, 18.04, 16.04, 14.04, and 12.04 (Ubuntu Notice), Debian provided updates for Debian 8 'Jessie' (version 1.3.16-4.4+deb8u1) and Debian 9 'Stretch' (version 1.3.16-5+deb9u1) (Debian LTS).