Steam Weak File Permissions Privilege Escalation

Vendor Website : http://store.steampowered.com/

 INDEX
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    1. CVE
    2. Background
    3. Description
    4. Impact
    5. Affected Products
    6. Solution
    7. Credit
    8. Disclosure Timeline


1. CVE
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    CVE: 2015-7985


2. BACKGROUND
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    Valve is the creator of Steam, the pioneering game platform that distributes and manages thousands of games directly to a community of more than 65 million players around the world.


3. DESCRIPTION
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    A privilege escalation vulnerability has been identified in that the Steam Microsoft Windows client software is installed with weak default permissions. These permissions grant read and write access to the Windows Users group for the install folder. This includes Steam.exe which is launched upon user login.


4. IMPACT
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    A low privileged user could modify the steam.exe binary and obtain code execution with elevated privileges upon an administrator login or execution of steam.exe

  
5. AFFECTED PRODUCTS
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    Only the following versions have been confirmed vulnerable:    

    Steam 2.10.91.91


6. SOLUTION
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    A workaround for the steam install folder includes removing write privileges from the Windows Users group. Additionally the vendor has provided security resources here: https://support.steampowered.com/kb_article.php?ref=1266-OAFV-8478


7. CREDIT
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    The vulnerability was discovered by Andrew Smith of Sword & Shield Enterprise Security.


8. DISCLOSURE TIMELINE
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    10-20-2015 - Vulnerability Discovered
    10-26-2015 - Vendor Informed
    10-26-2015 - Vendor Confirmed Receipt of Report
    10-27-2015 - CVE Requested
    10-28-2015 - Vendor Confirmed Public Disclosure
    11-12-2015 - Public Disclosure