Remote DoS in FreeBSD

Published: 2019-06-19

Risk	Medium
Patch available	YES
Number of vulnerabilities	1
CVE-ID	CVE-2019-5599
CWE-ID	CWE-400
Exploitation vector	Network
Public exploit	N/A
Vulnerable software Subscribe	FreeBSD Operating systems & Components / Operating system
Vendor	FreeBSD Foundation

Security Bulletin

This security bulletin contains one medium risk vulnerability.

1) Resource exhaustion

EUVDB-ID: #VU18846

Risk: Medium

CVSSv3.1: 5.2 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2019-5599

CWE-ID: CWE-400 - Resource exhaustion

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to an error when processing acknowledgements within the TCP loss detection algorithm RACK ("Recent ACKnowledgment"). A remote attacker can trigger resource exhaustion by sending specially crafted TCP packets to the affected system, which causes the several linked lists, used by RACK, to grow unbounded.

Successful exploitation of the vulnerability allows an attacker to perform denial of service attack (lower network performance, consume excessive CPU), but requires that system is compiled with RACK support.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

FreeBSD: 12.0

External links

http://www.freebsd.org/security/advisories/FreeBSD-SA-19:08.rack.asc

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.