An issue was discovered in BusyBox before 1.30.0. An out of bounds read in udhcp components (consumed by the DHCP server, client, and relay) allows a remote attacker to leak sensitive information from the stack by sending a crafted DHCP message. This is related to verification in udhcp_get_option() in networking/udhcp/common.c that 4-byte options are indeed 4 bytes.

References

• https://nvd.nist.gov/vuln/detail/CVE-2018-20679
• https://bugs.busybox.net/show_bug.cgi?id=11506
• https://busybox.net/news.html
• https://git.busybox.net/busybox/commit/?id=6d3b4bb24da9a07c263f3c1acf8df85382ff562c
• https://seclists.org/bugtraq/2019/Sep/7
• https://usn.ubuntu.com/3935-1/
• http://packetstormsecurity.com/files/154361/Cisco-Device-Hardcoded-Credentials-GNU-glibc-BusyBox.html
• http://seclists.org/fulldisclosure/2019/Sep/7