CVE-2018-20679

Severity: high (CVSS 7.5 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 7.7% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2019-01-09 · updated 2026-06-17
Weakness: CWE-125

Description

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.

Affected products

busybox: before 1.30.0 — fixed in 1.30.0
Canonical Ubuntu Linux: 14.04, 16.04, 18.04, 18.10

How to fix

Upgrade to a fixed version: busybox 1.30.0. Check the vendor advisory for mitigations.

References

http://packetstormsecurity.com/files/154361/Cisco-Device-Hardcoded-Credentials-GNU-glibc-BusyBox.html
http://seclists.org/fulldisclosure/2019/Sep/7
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
https://bugs.busybox.net/show_bug.cgi?id=11506
https://busybox.net/news.html
https://git.busybox.net/busybox/commit/?id=6d3b4bb24da9a07c263f3c1acf8df85382ff562c

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