Security Advisory

TLS-SSL - CVE-2016-2107
Published: July 22, 2018
Last Update: October 11, 2019

In May 2016, openssl.org released a security advisory detailing several security issues. The following vulnerabilities that may affect the TLS/SSL management plane of ACOS devices reported in that advisory are addressed in this document.

Item # Vulnerability ID Score Source Score Summary
1 CVE-2016-2107 CVSS 3.0 5.9 Med openssl: Padding oracle in AES-NI CBC MAC check [2]
2 91572 Nessus 2.6 Low OpenSSL AES-NI Padding Oracle MitM Information Disclosure [1]
Affected Releases

The table below indicates releases of ACOS exposed to these vulnerabilities and ACOS releases that address them. ACOS release families not indicated below are unaffected by these vulnerabilities.

Customers using affected ACOS releases can overcome vulnerability exposures by updating to the indicated resolved release. If the table does not list a corresponding resolved or unaffected release, then no ACOS release update is currently available.

Releases Affected Releases Resolved or Unaffected
4.1.100 – 4.1.100-P5 4.1.100-P5-SP1
4.1.0 – 4.1.0-P8 4.1.0-P9
3.1.0-P1 – 3.2.1-P1 3.2.2-P1
2.8.2-P10 – 2.8.2-Px 4.1.2, 4.1.4
2.7.2-P11 – 2.7.2-Px 4.1.0-P9, 4.1.1, 4.1.4
Workarounds and Mitigations

Common security best practices in the industry for network appliance management and control planes can enhance protection against remote malicious attacks. Limit the exploitable attack surface for critical, infrastructure, networking equipment through the use of access lists or firewall filters to and from only trusted, administrative networks or hosts.

Software Updates

Software updates that address these vulnerabilities are or will be published at the following URL:

Vulnerability Details

The following table shares brief descriptions of the vulnerabilities addressed in this document.

Vulnerability ID Vulnerability Description

The AES-NI implementation in OpenSSL before 1.0.1t and 1.0.2 before 1.0.2h does not consider memory allocation during a certain padding check, which allows remote attackers to obtain sensitive cleartext information via a padding-oracle attack against an AES CBC session. NOTE: this vulnerability exists because of an incorrect fix for CVE-2013-0169.


The remote host is affected by a man-in-the-middle (MitM) information disclosure vulnerability due to an error in the implementation of ciphersuites that use AES in CBC mode with HMAC-SHA1 or HMAC-SHA256.

The implementation is specially written to use the AES acceleration available in x86/amd64 processors (AES-NI). The error messages returned by the server allow allow a man-in-the-middle attacker to conduct a padding oracle attack, resulting in the ability to decrypt network traffic.

Reference: CVE-2016-2107
Evidence: Plugin Output: Nessus was able to trigger a RECORD_OVERFLOW alert in the remote service by sending a crafted SSL "Finished" message.

Related Links

The following table shares brief descriptions for the vulnerabilities addressed in this document.

Ref # General Link
[1] Nessus: OpenSSL AES-NI Padding Oracle MitM Information Disclosure
[2] NIST NVD, CVE-2016-2107


Modification History
Revision Date Description
1.0 July 22, 2018

Initial Publication

2.0 October 11, 2019

Added 4.1.100 release family.

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