CVE-2017-17439

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.

• CWE-476

• http://h5l.org/advisories.html?show=2017-12-08
• http://www.h5l.org/pipermail/heimdal-announce/2017-December/000008.html
• http://www.h5l.org/pipermail/heimdal-discuss/2017-August/000259.htmlThird Party Advisory
• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=878144Issue Tracking, Mailing List, Third Party Advisory
• https://github.com/heimdal/heimdal/commit/1a6a6e462dc2ac6111f9e02c6852ddec4849b887Third Party Advisory
• https://github.com/heimdal/heimdal/issues/353Patch, Third Party Advisory
• https://www.debian.org/security/2017/dsa-4055Third Party Advisory
• http://h5l.org/advisories.html?show=2017-12-08
• http://www.h5l.org/pipermail/heimdal-announce/2017-December/000008.html
• http://www.h5l.org/pipermail/heimdal-discuss/2017-August/000259.htmlThird Party Advisory
• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=878144Issue Tracking, Mailing List, Third Party Advisory
• https://github.com/heimdal/heimdal/commit/1a6a6e462dc2ac6111f9e02c6852ddec4849b887Third Party Advisory
• https://github.com/heimdal/heimdal/issues/353Patch, Third Party Advisory
• https://www.debian.org/security/2017/dsa-4055Third Party Advisory

Published

Dec 6, 2017

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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