CVE-2017-17439

Publication date 6 December 2017

Last updated 25 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

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.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
heimdal	18.10 cosmic	Not affected
	18.04 LTS bionic	Not affected
	17.10 artful	Ignored end of life
	17.04 zesty	Ignored end of life
	16.04 LTS xenial	Not affected
	14.04 LTS trusty	Not affected

Notes

mdeslaur

vulnerability introduced in 7.0 heimdal-kdc package is in universe

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
heimdal	Upstream: 1a6a6e4

Severity score breakdown

Parameter	Value
Base score	7.5 · High
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality	None
Integrity impact	None
Availability impact	High
Vector	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H