Amazon Linux AMI update for openssh

Published: 2017-10-03 | Updated: 2023-03-20

Risk	Medium
Patch available	YES
Number of vulnerabilities	5
CVE-ID	CVE-2016-10009 CVE-2016-6210 CVE-2016-6515 CVE-2016-10011 CVE-2016-10012
CWE-ID	CWE-20 CWE-200 CWE-400 CWE-264 CWE-119
Exploitation vector	Network
Public exploit	Public exploit code for vulnerability #1 is available. Public exploit code for vulnerability #2 is available. Public exploit code for vulnerability #3 is available.
Vulnerable software Subscribe	Amazon Linux AMI Operating systems & Components / Operating system
Vendor	Amazon Web Services

Security Bulletin

This security bulletin contains information about 5 vulnerabilities.

1) Improper input validation

EUVDB-ID: #VU2015

Risk: Low

CVSSv3.1: 7.5 [CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2016-10009

CWE-ID: CWE-20 - Improper input validation

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to execute arbitrary code on vulnerable ssh client.

The vulnerability exists due to incorrect handling of data passed to PKCS#11 module within ssh-agent. A remote attacker with control over sshd service can execute arbitrary code on vulnerable client.

Successful exploitation of this vulnerability may allow a remote attacker to execute arbitrary code on vulnerable client system but requires that client is connected to malicious SSH server.

Mitigation

Update the affected packages.

i686:
    openssh-ldap-7.4p1-11.68.amzn1.i686
    pam_ssh_agent_auth-0.10.3-1.11.68.amzn1.i686
    openssh-cavs-7.4p1-11.68.amzn1.i686
    openssh-7.4p1-11.68.amzn1.i686
    openssh-debuginfo-7.4p1-11.68.amzn1.i686
    openssh-keycat-7.4p1-11.68.amzn1.i686
    openssh-server-7.4p1-11.68.amzn1.i686
    openssh-clients-7.4p1-11.68.amzn1.i686

src:
    openssh-7.4p1-11.68.amzn1.src

x86_64:
    openssh-ldap-7.4p1-11.68.amzn1.x86_64
    openssh-server-7.4p1-11.68.amzn1.x86_64
    openssh-7.4p1-11.68.amzn1.x86_64
    openssh-keycat-7.4p1-11.68.amzn1.x86_64
    pam_ssh_agent_auth-0.10.3-1.11.68.amzn1.x86_64
    openssh-cavs-7.4p1-11.68.amzn1.x86_64
    openssh-debuginfo-7.4p1-11.68.amzn1.x86_64
    openssh-clients-7.4p1-11.68.amzn1.x86_64

Vulnerable software versions

Amazon Linux AMI: All versions

External links

http://alas.aws.amazon.com/ALAS-2017-898.html

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. However, proof of concept for this vulnerability is available.

2) User enumeration via covert timing channel

EUVDB-ID: #VU255

Risk: Medium

CVSSv3.1: 4.9 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N/E:F/RL:O/RC:C]

CVE-ID: CVE-2016-6210

CWE-ID: CWE-200 - Information exposure

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to enumerate users on system.

The vulnerability exists in most systems where the Blowfish algorithm runs faster than SHA256/SHA512. A remote unauthenticated attacker can determine valid usernames by sending a specially crafted request with a large password (approximately 10,000 characters) to the target ssh daemon. On systems where a valid user's password has been hashed with SHA256/SHA512, the response time will be shorter for a non-existent username than for a valid username.

Successful exploitation of this vulnerability may result in disclosure or user logins.

Mitigation

Update the affected packages.

i686:
    openssh-ldap-7.4p1-11.68.amzn1.i686
    pam_ssh_agent_auth-0.10.3-1.11.68.amzn1.i686
    openssh-cavs-7.4p1-11.68.amzn1.i686
    openssh-7.4p1-11.68.amzn1.i686
    openssh-debuginfo-7.4p1-11.68.amzn1.i686
    openssh-keycat-7.4p1-11.68.amzn1.i686
    openssh-server-7.4p1-11.68.amzn1.i686
    openssh-clients-7.4p1-11.68.amzn1.i686

src:
    openssh-7.4p1-11.68.amzn1.src

x86_64:
    openssh-ldap-7.4p1-11.68.amzn1.x86_64
    openssh-server-7.4p1-11.68.amzn1.x86_64
    openssh-7.4p1-11.68.amzn1.x86_64
    openssh-keycat-7.4p1-11.68.amzn1.x86_64
    pam_ssh_agent_auth-0.10.3-1.11.68.amzn1.x86_64
    openssh-cavs-7.4p1-11.68.amzn1.x86_64
    openssh-debuginfo-7.4p1-11.68.amzn1.x86_64
    openssh-clients-7.4p1-11.68.amzn1.x86_64

Vulnerable software versions

Amazon Linux AMI: All versions

External links

http://alas.aws.amazon.com/ALAS-2017-898.html

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. However, a fully functional exploit for this vulnerability is available.

3) Consuming excessive CPU resources on the target system

EUVDB-ID: #VU252

Risk: Medium

CVSSv3.1: 7.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2016-6515

CWE-ID: CWE-400 - Resource exhaustion

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to consume excessive CPU resources on the target system.

The vulnerability exists in the crypt(3) function, which accepts passwords longer that 1024 characters in auth_password() function in the auth_passwd.c . A remote unauthenticated attacker can submit a very long string as a password and consume excessive CPU resources.

Successful exploitation of this vulnerability may result in denial of service.

Mitigation

Update the affected packages.

i686:
    openssh-ldap-7.4p1-11.68.amzn1.i686
    pam_ssh_agent_auth-0.10.3-1.11.68.amzn1.i686
    openssh-cavs-7.4p1-11.68.amzn1.i686
    openssh-7.4p1-11.68.amzn1.i686
    openssh-debuginfo-7.4p1-11.68.amzn1.i686
    openssh-keycat-7.4p1-11.68.amzn1.i686
    openssh-server-7.4p1-11.68.amzn1.i686
    openssh-clients-7.4p1-11.68.amzn1.i686

src:
    openssh-7.4p1-11.68.amzn1.src

x86_64:
    openssh-ldap-7.4p1-11.68.amzn1.x86_64
    openssh-server-7.4p1-11.68.amzn1.x86_64
    openssh-7.4p1-11.68.amzn1.x86_64
    openssh-keycat-7.4p1-11.68.amzn1.x86_64
    pam_ssh_agent_auth-0.10.3-1.11.68.amzn1.x86_64
    openssh-cavs-7.4p1-11.68.amzn1.x86_64
    openssh-debuginfo-7.4p1-11.68.amzn1.x86_64
    openssh-clients-7.4p1-11.68.amzn1.x86_64

Vulnerable software versions

Amazon Linux AMI: All versions

External links

http://alas.aws.amazon.com/ALAS-2017-898.html

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. However, proof of concept for this vulnerability is available.

4) Information disclosure

EUVDB-ID: #VU2068

Risk: Low

CVSSv3.1: 4.8 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2016-10011

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

Exploit availability: No

Description

The vulnerability allows a local user to gain access to potentially sensitive information.

The vulnerability exists due to an error in authfile.c, which may allow a local authenticated user to obtain host private key material.

Successful exploitation of this vulnerability may allow a local user to gain access to otherwise restricted information.

Mitigation

Update the affected packages.

i686:
    openssh-ldap-7.4p1-11.68.amzn1.i686
    pam_ssh_agent_auth-0.10.3-1.11.68.amzn1.i686
    openssh-cavs-7.4p1-11.68.amzn1.i686
    openssh-7.4p1-11.68.amzn1.i686
    openssh-debuginfo-7.4p1-11.68.amzn1.i686
    openssh-keycat-7.4p1-11.68.amzn1.i686
    openssh-server-7.4p1-11.68.amzn1.i686
    openssh-clients-7.4p1-11.68.amzn1.i686

src:
    openssh-7.4p1-11.68.amzn1.src

x86_64:
    openssh-ldap-7.4p1-11.68.amzn1.x86_64
    openssh-server-7.4p1-11.68.amzn1.x86_64
    openssh-7.4p1-11.68.amzn1.x86_64
    openssh-keycat-7.4p1-11.68.amzn1.x86_64
    pam_ssh_agent_auth-0.10.3-1.11.68.amzn1.x86_64
    openssh-cavs-7.4p1-11.68.amzn1.x86_64
    openssh-debuginfo-7.4p1-11.68.amzn1.x86_64
    openssh-clients-7.4p1-11.68.amzn1.x86_64

Vulnerable software versions

Amazon Linux AMI: All versions

External links

http://alas.aws.amazon.com/ALAS-2017-898.html

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.

Is there known malware, which exploits this vulnerability?

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

5) Buffer overflow

EUVDB-ID: #VU2075

Risk: Low

CVSSv3.1: 6.8 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2016-10012

CWE-ID: CWE-119 - Memory corruption

Exploit availability: No

Description

The vulnerability allows a local user to execute arbitrary code on vulnerable system with root privileges.

The vulnerability exists in sshd due to a flaw in boundary checks in the shared memory manager that may be skipped by some optimizing compilers. A local user can trigger memory corruption and execute arbitrary code with root privileges. The issue is related to m_zback and m_zlib data structures.

Successful exploitation of this vulnerability may allow a local user to elevate privileges.

Mitigation

Update the affected packages.

i686:
    openssh-ldap-7.4p1-11.68.amzn1.i686
    pam_ssh_agent_auth-0.10.3-1.11.68.amzn1.i686
    openssh-cavs-7.4p1-11.68.amzn1.i686
    openssh-7.4p1-11.68.amzn1.i686
    openssh-debuginfo-7.4p1-11.68.amzn1.i686
    openssh-keycat-7.4p1-11.68.amzn1.i686
    openssh-server-7.4p1-11.68.amzn1.i686
    openssh-clients-7.4p1-11.68.amzn1.i686

src:
    openssh-7.4p1-11.68.amzn1.src

x86_64:
    openssh-ldap-7.4p1-11.68.amzn1.x86_64
    openssh-server-7.4p1-11.68.amzn1.x86_64
    openssh-7.4p1-11.68.amzn1.x86_64
    openssh-keycat-7.4p1-11.68.amzn1.x86_64
    pam_ssh_agent_auth-0.10.3-1.11.68.amzn1.x86_64
    openssh-cavs-7.4p1-11.68.amzn1.x86_64
    openssh-debuginfo-7.4p1-11.68.amzn1.x86_64
    openssh-clients-7.4p1-11.68.amzn1.x86_64

Vulnerable software versions

Amazon Linux AMI: All versions

External links

http://alas.aws.amazon.com/ALAS-2017-898.html

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.

Is there known malware, which exploits this vulnerability?

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