CVE-2017-17439: Debian Linux

High severity, CVSS 7.5. EPSS: 3.4% chance of exploitation in the next 30 days.

In Heimdal through 7.4, remote unauthenticated attackers are able to crash the KDC by sending a crafted UDP packet containing empty data fields for client name or realm. The parser would unconditionally dereference NULL pointers in that case, leading to a segmentation fault. This is related to the _kdc_as_rep function in kdc/kerberos5.c and the der_length_visible_string function in lib/asn1/der_length.c.

Affected products

• Debian Debian Linux: version 9.0 only
• Heimdal Project Heimdal: up to and including 7.4.0

Published 2017-12-06. Last modified 2026-06-17.