Microsoft Outlook OLE content retrieval vulnerability

Discussion in 'Tech news' started by jasonX, Apr 12, 2018.

  1. jasonX

    jasonX Giveaways Moderator Staff Member

    Microsoft Outlook OLE content retrieval vulnerability

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    Overview
    When a Rich Text (RTF) email is previewed in Microsoft Outlook, remotely-hosted OLE content is retrieved without requiring any additional user interaction. This can leak private information including the user's password hash, which may be cracked by an attacker.

    Description
    Microsoft Outlook will automatically retrieve remote OLE content when an RTF email is previewed. When remote OLE content is hosted on a SMB/CIFS server, the Windows client system will attempt to authenticate with the server using single sign-on (SSO). This may leak the user's IP address, domain name, user name, host name, and password hash. If the user's password is not complex enough, then an attacker may be able to crack the password in a short amount of time.

    User is duped into previewing an RTF email message with Microsoft Outlook, a remote, unauthenticated attacker may be able to obtain the victim's ip address, domain name, user name, host name, and password hash. Such password hash may be cracked offline. Said vulnerability may be combined with other vulnerabilities to modify the impact.

    Solution

    Apply Microsoft update for CVE-2018-0950
    This vulnerability is addressed in the Microsoft update for CVE-2018-0950. This update prevents Outlook from automatically initiating SMB connections when an RTF email is previewed. Note that other techniques requiring additional user interaction will still function after this patch is installed. For example, if an email contains a UNC link, like \\attacker\foo, Outlook will automatically make this link clickable. If a user clicks such a link, the impact will be the same as with this vulnerability. For this reason, please also consider the following workarounds.

    Block inbound and outbound SMB connections at your network border

    This can be accomplished by blocking ports 445/tcp, 137/tcp, 139/tcp, as well as 137/udp and 139/udp.

    Block NTLM Single Sign-on (SSO) authentication
    Block NTLM Single Sign-on (SSO) authentication, as specified in Microsoft Security Advisory ADV170014. Starting with Windows 10 and Server 2016, if the EnterpriseAccountSSO registry value is created and set to 0, SSO authentication will be disabled for external and unspecified network resources. With this registry change, accessing SMB resources is still allowed, but external and unspecified SMB resources will require the user to enter credentials as opposed to automatically attempting to use the hash of the currently logged-on user.

    Use complex passwords
    Assume that at some point your client system will attempt to make an SMB connection to an attacker's server. For this reason, make sure that any Windows login has a sufficiently complex password so that it is resistant to cracking.

    The following two strategies can help achieve this goal:
    Use a password manager to help generate complex random passwords. This strategy can help ensure the use of unique passwords across resources that you use, and it can ensure that the passwords are of a sufficient complexity and randomness.

    Use longer passphrases (with mixed-case letters, numbers and symbols) instead of passwords. This strategy can produce memorable credentials that do not require additional software to store and retrieve.

    CVE-2018-0950 | Microsoft Office Information Disclosure Vulnerability
    https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2018-0950


    Source
    https://www.kb.cert.org/vuls/id/974272

    Related Sources
    https://thehackernews.com/2018/04/outlook-smb-vulnerability.html

    https://tools.cisco.com/security/center/viewAlert.x?alertId=57334

    https://www.bleepingcomputer.com/news/security/microsoft-half-patches-old-outlook-vulnerability/
     
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