[Snort-2003-001] Buffer overflow in Snort RPC preprocessor (fwd)

From: Dave Ahmad (daat_private)
Date: Mon Mar 03 2003 - 15:23:22 PST

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    David Mirza Ahmad
    Symantec
    
    "sabbe dhamma anatta"
    
    0x26005712
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    Snort Vulnerability Advisory [SNORT-2003-001]
    
    Date: 2003-03-03
    
    Affected Snort Versions:
    
    Any version starting with version 1.8 to those before 2003-03-03 1PM/
    US/Eastern including 1.9.0 and CVS HEAD (Snort 2.0beta)
    
    Synopsis:
    
    A buffer overflow has been found in the snort RPC normalization
    routines by ISS X-Force.  This can cause snort to execute arbitrary
    code embedded within sniffed network packets. This preprocessor is
    enabled by default.
    
    Snort 1.9.1 has been released to resolve this issue. For users using
    CVS HEAD, a fix has been committed to the source tree.
    
    Mitigation:
    
    If you are in an environment that can not upgrade snort immediately,
    comment out the line in your snort.conf that begins:
    
    preprocessor rpc_decode
    
    and replace it with
    
    # preprocessor rpc_decode
    
    Details:
    
    When the rpc decoder normalizes fragmented RPC records, it incorrectly
    checks the lengths of what is being normalized against the current
    packet size.
    
    The rpc decoder in Snort 1.9.1 and above contains new alert options
    that can be used to help detect this attack
    
    Option                    Default State
    
    alert_fragments           INACTIVE
    alert_large_fragments     ACTIVE
    alert_incomplete          ACTIVE
    alert_multiple_requests   ACTIVE
    
    
    The first option will alert on any rpc fragmented record it finds.
    Large fragments will alert when the reassembled fragment record will
    exceed the current packet length.  The incomplete record will alert
    when there is a partial record found.  The alert_multiple_requests will
    alert when we find more than one RPC request per packet ( or
    reassembled packet ).
    
    Download Locations:
    
    Sourcefire has acquired additional bandwidth and hosting to aid users
    wishing to upgrade their Snort implementation.  Binaries are currently
    not available, this is a source release only at this time.  As new
    binaries become available they will be added to the site.
    
    Source code: http://www.snort.org/dl/snort-1.9.1.tar.gz
    GPG Signatures: http://www.snort.org/dl/snort-1.9.1.tar.gz.asc
    
    CVS HEAD (Snort 2.0beta)  has been fixed as well.
    
    
    - --
    Martin Roesch - Founder/CTO, Sourcefire Inc. - (410)290-1616
    Sourcefire: Snort-based Enterprise Intrusion Detection Infrastructure
    roeschat_private - http://www.sourcefire.com
    Snort: Open Source Network IDS - http://www.snort.org
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