NULL pointer dereference in heimdal (Alpine package)

1) NULL pointer dereference

EUVDB-ID: #VU33177

Risk: Medium

CVSSv3.1: 6.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2017-17439

CWE-ID: CWE-476 - NULL Pointer Dereference

Exploit availability: No

Description

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.

Mitigation

Install update from vendor's website.

Vulnerable software versions

heimdal (Alpine package): 7.1.0-r0 - 7.1.0-r1

External links

http://git.alpinelinux.org/aports/commit/?id=7f6e6b03d2536a389bb79a29915bd3a8fe881517
http://git.alpinelinux.org/aports/commit/?id=e6b1fa7dad551ad0f3cbb54319d7b8d38ed40ddb
http://git.alpinelinux.org/aports/commit/?id=aa2d24fab1e16e497512004aa40a11c032fcab73
http://git.alpinelinux.org/aports/commit/?id=d7f01c593b1ee60783bd9bf1b13f1ef234896a10
http://git.alpinelinux.org/aports/commit/?id=098600ef518cef710f190712a9a7be6b53179d5c
http://git.alpinelinux.org/aports/commit/?id=5f79fcd7bde881eaef40a645eff0b6bd42f272a4

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.