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Vulnerability record · CVE-2017-17439 · published 6 December 2017

CVE-2017-17439: Debian linux null pointer dereference vulnerability

Debian · Debian Linux

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.

7.5 CVSS 3.0 High EPSS 3.4% · top 11.5% CWE-476 · NULL pointer dereference
7.5CVSS 3.0 base score, v2 5.0
3.4%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
14References
17 Jun 2026Last modified by NVD

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.

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
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.html Third Party Advisory
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=878144 Issue TrackingMailing ListThird Party Advisory
https://github.com/heimdal/heimdal/commit/1a6a6e462dc2ac6111f9e02c6852ddec4849b887 Third Party Advisory
https://github.com/heimdal/heimdal/issues/353 PatchThird Party Advisory
https://www.debian.org/security/2017/dsa-4055 Third 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.html Third Party Advisory
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=878144 Issue TrackingMailing ListThird Party Advisory
https://github.com/heimdal/heimdal/commit/1a6a6e462dc2ac6111f9e02c6852ddec4849b887 Third Party Advisory
https://github.com/heimdal/heimdal/issues/353 PatchThird Party Advisory
https://www.debian.org/security/2017/dsa-4055 Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2017-17439), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.