Privilege escalation in OpenSSH

Published: 2019-10-09 | Updated: 2019-10-24
Severity Low
Patch available YES
Number of vulnerabilities 1
CVE ID CVE-2019-16905
CWE ID CWE-190
Exploitation vector Local
Public exploit N/A
Vulnerable software OpenSSH Subscribe
Vendor OpenSSH

Security Advisory

This security advisory describes one low risk vulnerability.

1) Integer overflow

Severity: Low

CVSSv3: 6.1 [CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C] [PCI]

CVE-ID: CVE-2019-16905

CWE-ID: CWE-190 - Integer Overflow or Wraparound

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to integer overflow within the XMSS key parsing algorithm. A local user can configure the server or client to use a specially crafted XMSS private key, trigger integer overflow and execute arbitrary code on the target system with elevated privileges.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

OpenSSH: 7.8p1, 7.9p1, 8.0p1

CPE External links

https://0day.life/exploits/0day-1009.html
https://bugzilla.suse.com/show_bug.cgi?id=1153537
https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/sshkey-xmss.c
https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/sshkey-xmss.c.diff?r1=1.5&r2=1.6&f=h
https://security.netapp.com/advisory/ntap-20191024-0003/
https://ssd-disclosure.com/archives/4033/ssd-advisory-openssh-pre-auth-xmss-integer-overflow
https://www.openssh.com/releasenotes.html
https://www.openwall.com/lists/oss-security/2019/10/09/1

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

The attacker would have to login to the system and perform certain actions in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

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