SB2017120615 - NULL pointer dereference in heimdal
Published: December 6, 2017 Updated: August 3, 2020
Security Bulletin ID
SB2017120615
Severity
Medium
Patch available
YES
Number of vulnerabilities
1
Exploitation vector
Remote access
Highest impact
Denial of service
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 1 security vulnerability.
1) NULL pointer dereference (CVE-ID: CVE-2017-17439)
The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.
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.
Remediation
Install update from vendor's website.
References
- 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
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=878144
- https://github.com/heimdal/heimdal/commit/1a6a6e462dc2ac6111f9e02c6852ddec4849b887
- https://github.com/heimdal/heimdal/issues/353
- https://www.debian.org/security/2017/dsa-4055