An exploitable information leak vulnerability exists in the ustream-ssl library of OpenWrt, versions 18.06.4 and 15.05.1. When connecting to a remote server, the server's SSL certificate is checked but no action is taken when the certificate is invalid. An attacker could exploit this behavior by performing a man-in-the-middle attack, providing any certificate, leading to the theft of all the data sent by the client during the first request. After an SSL connection is initialized via _ustream_ssl_init, and after any data (e.g. the client's HTTP request) is written to the stream using ustream_printf, the code eventually enters the function __ustream_ssl_poll, which is used to dispatch the read/write events

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-5101
• https://talosintelligence.com/vulnerability_reports/TALOS-2019-0893