CVE-2020-17469: Butok Fnet

High severity, CVSS 7.5. EPSS: 3% chance of exploitation in the next 30 days.

An issue was discovered in FNET through 4.6.4. The code for IPv6 fragment reassembly tries to access a previous fragment starting from a network incoming fragment that still doesn't have a reference to the previous one (which supposedly resides in the reassembly list). When faced with an incoming fragment that belongs to a non-empty fragment list, IPv6 reassembly must check that there are no empty holes between the fragments: this leads to an uninitialized pointer dereference in _fnet_ip6_reassembly in fnet_ip6.c, and causes Denial-of-Service.

Affected products

• Butok Fnet: up to and including 4.6.4

Published 2020-12-11. Last modified 2026-06-17.