NetworkManager-l2tp Privilege Escalation via pppd Username Injection
NetworkManager-l2tp through 1.52.4, fixed in 1.52.6, contains a privilege escalation vulnerability that allows local users with permission to create VPN connections to execute arbitrary code as root by injecting pppd options through a crafted VPN username. Attackers can embed a double-quote character or whitespace in the username to break out of the pppd options file quoting context and include the pppd plugin directive, causing the privileged pppd process to load an attacker-controlled shared object.
The code in pppd that formats a response to a PEAP Request packet in peap_response() copies an entire TLS record of up to 16384 bytes into the fixed global buffer outpacket_buf
without checking the available space and without implementing outgoing
PEAP fragmentation. Thus a pppd process connecting to a server which
requests PEAP authentication can be induced to corrupt global static
data following the outpacket_buf array, most likely causing incorrect behavior or a crash.
NetworkManager-l2tp: local privilege escalation via ipsec.conf injection
A flaw was found in NetworkManager-l2tp. The plugin writes attacker-controlled VPN connection properties (vpn.data and vpn.secrets values) unescaped into a generated ipsec.conf file that pluto loads as root. A local unprivileged user can create and activate their own L2TP VPN profile containing a newline-injected leftupdown directive; pluto executes that command as root when the IKE security association is established, resulting in local privilege escalation. This is the same bug class as CVE-2018-10900 (NetworkManager-vpnc).