Tag: Vulnerability

Advisory on Badlock Vulnerability

badlock

This is a security advisory on the Badlock Bug.

What is Badlock?

Samba is an important component to seamlessly integrate Linux/Unix Servers and Desktops into Active Directory environments. It can function both as a domain controller and as a regular domain member. On April 12th, 2016 Badlock, a crucial security bug in Windows and Samba was disclosed. The security vulnerabilities can be mostly categorized as man-in-the-middle or denial of service attacks.

Man-in-the-middle (MITM) attacks:

There are several MITM attacks that can be performed against a variety of protocols used by Samba. These would permit execution of arbitrary Samba network calls using the context of the intercepted user. Impact examples of intercepting administrator network traffic:

  • Samba AD server – view or modify secrets within an AD database, including user password hashes, or shutdown critical services.
  • Standard Samba server – modify user permissions on files or directories.

Denial-of-Service (DoS) attacks:

Samba services are vulnerable to a denial of service from an attacker with remote network connectivity to the Samba service. Microsoft has addressed this in MS16-047. This vulnerability can be used to login as another user for applications that use the SAMR or LSAD protocol. All versions of Windows are affected.

Who is Vulnerable?

Samba Application running on Linux/Unix Systems

  • 3.6.x,
  • 4.0.x,
  • 4.1.x,
  • 4.2.0-4.2.9,
  • 4.3.0-4.3.6,
  • 4.4.0

Windows

All supported editions of Windows Vista, Windows Server 2008, Windows 7, Windows Server 2008 R2, Windows 8.1, Windows Server 2012, Windows Server 2012 R2, Windows RT 8.1, and Windows 10.

Associated CVEs

Badlock for Samba is referenced by CVE-2016-2118 (SAMR and LSA man in the middle attacks possible) and for Windows by CVE-2016-0128 / MS16-047 (Windows SAM and LSAD Downgrade Vulnerability).

There are additional CVEs related to Badlock. Those are:

  • CVE-2015-5370 (Multiple errors in DCE-RPC code)
  • CVE-2016-2110 (Man in the middle attacks possible with NTLMSSP)
  • CVE-2016-2111 (NETLOGON Spoofing Vulnerability)
  • CVE-2016-2112 (LDAP client and server don’t enforce integrity)
  • CVE-2016-2113 (Missing TLS certificate validation)
  • CVE-2016-2114 (“server signing = mandatory” not enforced)
  • CVE-2016-2115 (SMB IPC traffic is not integrity protected)

How to check if server is vulnerable?

A server is vulnerable to BADLOCK if:

  • It is running any of the above mentioned versions of SAMBA
  • For vulnerable Windows versions refer the following link:

https://technet.microsoft.com/library/security/MS16-047

How to fix

For Samba service running on Linux/Unix systems, apply the patches provided by the Samba Team and SerNet for EnterpriseSAMBA / SAMBA+ immediately.

Patched versions are (both the interim and final security release have the patches):

  • 4.2.10 / 4.2.11,
  • 4.3.7 / 4.3.8,
  • 4.4.1 / 4.4.2.

For Windows Installations, refer following link for patch details:

https://technet.microsoft.com/library/security/MS16-047

 

References and Useful Links

http://badlock.org/

https://www.samba.org/samba/latest_news.html#4.4.2

https://www.samba.org/samba/security/CVE-2016-2118.html

https://technet.microsoft.com/library/security/MS16-047

For more information or a vulnerability scan, please contact us at avantedge@pkfmalaysia.com.

DROWN Vulnerability: Cross-protocol attack on TLS using SSLv2

This is a security advisory on the DROWN Attack (CVE-2016-0800).

What is DROWN Attack (CVE-2016-0800)

DROWN, stands for “Decrypting RSA with Obsolete and Weakened eNcryption”, is a serious vulnerability that affects HTTPS and other services that rely on SSL and TLS, some of the essential cryptographic protocols for Internet security. These protocols allow everyone on the Internet to browse the web, use email, shop online, and send instant messages without third-parties being able to read the communication.

Any communication between users and the server, typically includes, but is not limited to, usernames and passwords, credit card numbers, emails, instant messages, and other sensitive information. Under some common scenarios, an attacker can also impersonate a secure website and intercept or change the content the user sees.

A group of security researchers discovered that SSLv2 (Secure Sockets Layer protocol version 2.0) is vulnerable to the Bleichenbacher RSA padding oracle attack, which can be used to decrypt RSA cipher text without the knowledge of the matching private RSA key. This can be done by observing responses from a server that has the private key and performs the decryption of attacker-provided cipher texts using that key. A cross-protocol attack was discovered that could lead to decryption of TLS sessions by using a server supporting SSLv2 and export cipher suites such as Bleichenbacher RSA padding oracle. The cross-protocol attack allows decryption of SSL/TLS sessions using newer protocol versions – SSLv3 or any current TLS (Transport Layer Security) version (1.0 – 1.2) – using this SSLv2 weakness. Note that traffic between clients and non-vulnerable servers can be decrypted provided another server supporting SSLv2 and EXPORT ciphers (even with a different protocol such as SMTP, IMAP or POP) shares the RSA keys of the non-vulnerable server (CVE-2016-0800. This flaw is SSLv2 protocol issue and affects all implementations of the protocol.

Who is Vulnerable?

Websites, mail servers, and other TLS-dependent services are at risk for the DROWN attack.

How to check if server is vulnerable?

A server is vulnerable to DROWN if:

  • It allows SSLv2 connections. This is surprisingly common, due to misconfiguration and inappropriate default settings.
  • Its private key is used on any other server that allows SSLv2 connections, even for another protocol.

How to fix

It is recommend to:

  • Ensure that servers private keys are not used anywhere with server software that allows SSLv2 connections. This includes web servers, SMTP servers, IMAP and POP servers, and any other software that supports SSL/TLS.
  • OpenSSL 1.0.2 users should upgrade to 1.0.2g, OpenSSL 1.0.1 users should upgrade to 1.0.1s
  • Disable the complete support of SSLv2 by following the vendor’s advisory:
    Internet Information Services (IIS)

    Apache

    Postfix

    Nginx

    IBM HTTP Server

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