Permissions, Privileges, and Access Controls in openssh (Alpine package)

1) Permissions, Privileges, and Access Controls

EUVDB-ID: #VU33288

Risk: High

CVSSv3.1: 7.1 [CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2015-5600

CWE-ID: CWE-264 - Permissions, Privileges, and Access Controls

Exploit availability: No

Description

The vulnerability allows a remote non-authenticated attacker to #BASIC_IMPACT#.

The kbdint_next_device function in auth2-chall.c in sshd in OpenSSH through 6.9 does not properly restrict the processing of keyboard-interactive devices within a single connection, which makes it easier for remote attackers to conduct brute-force attacks or cause a denial of service (CPU consumption) via a long and duplicative list in the ssh -oKbdInteractiveDevices option, as demonstrated by a modified client that provides a different password for each pam element on this list.

Mitigation

Install update from vendor's website.

Vulnerable software versions

openssh (Alpine package): 6.1_p1-r0 - 6.4_p1-r2

External links

http://git.alpinelinux.org/aports/commit/?id=8a07923212fef85b959a7a5d33641b887bb28926
http://git.alpinelinux.org/aports/commit/?id=3885568b0e267af8bd7ce20f4c0337c84312da01
http://git.alpinelinux.org/aports/commit/?id=349ad37b3400ed4f7f3fb02db6fec33d252dd704
http://git.alpinelinux.org/aports/commit/?id=4c781145fea2f72a16dcf5acd51e426850ef540a
http://git.alpinelinux.org/aports/commit/?id=f313c8ea055322f60121a3baf75c0d16ea154978

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.