Steam Weak File Permissions Privilege Escalation

[ajs@xxxxxxxxxxxxxxx]

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