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Category:   Application (Generic)  >   Splunk Vendors:   Splunk Inc.
Splunk Flaw in spunkd Lets Remote Users Deny Service
SecurityTracker Alert ID:  1027784
SecurityTracker URL:
CVE Reference:   GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Nov 19 2012
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  Exploit Included:  Yes  
Version(s): 4.0 - 4.3.4
Description:   A vulnerability was reported in Splunk. A remote user can cause denial of service conditions.

A remote user can send a packet with a specially crafted '__s2s_capabilities' field value to cause the target splunkd service to become unavailable.

Systems configured for splunktcp are affected (not the default configuration).

The vendor was notified on September 3, 2012.

Alexander Klink and Moritz Jodeit of n.runs AG reported this vulnerability.

Impact:   A remote user can cause splunkd to become unavailable.
Solution:   The vendor has issued a fix (4.3.5, 5.0).

The vendor's advisory is available at:

Vendor URL: (Links to External Site)
Cause:   Not specified
Underlying OS:  Linux (Any), UNIX (AIX), UNIX (FreeBSD), UNIX (HP/UX), UNIX (macOS/OS X), UNIX (Solaris - SunOS), Windows (Any)

Message History:   None.

 Source Message Contents

Subject:  n.runs-SA-2012.004 - SPLUNK Unauthenticated remote DoS

n.runs AG
Vendors:            Splunk Inc.,
Product:            Splunk 4.0 - 4.3.4
Vulnerability:      Unauthenticated remote denial of service against splunkd
Tracking IDs:       SPL-55521
Vendor communication:
2012/09/03 Reported the issue via Splunk's website
2012/09/04 Splunk responds and assigns tracking ID, plans fix for 4.3.5
2012/10/25 Splunk informs us that 5.0 will be available on November 1st
           and 4.3.5 on November 15th. Proposes to defer announcement of
           the vulnerability to ensure that people aren't forced to move
           to a new major release in order to mitigate. n.runs agrees.   

When a splunktcp-input (for use in Splunk-to-Splunk communication) is
configured, an attacker can send an initial packet with a malformed
'__s2s_capabilities' field. This leads to a crash of the splunkd daemon
making the splunktcp-input unavailable. If the Splunk web-interface is
running on the same host, it will be unavailable, too as it needs to
communicate with splunkd.


An example packet looks like this (__s2s_capabilities is just 'A' here):

When this packet is sent multiple times, splunkd eventually crashes with a
crash log similar to this one:

[build 128297] 2012-08-30 13:34:01
 Access violation, cannot read at address [0x00006A62]  Exception address:
[0x6FC4500A]  Crashing thread: TcpInputProcessor
    ContextFlags:  [0x0001007F]
    Dr0:  [0x00000000]
    Dr1:  [0x00000000]
    Dr2:  [0x00000000]
    Dr3:  [0x00000000]
    Dr6:  [0x00000000]
    Dr7:  [0x00000000]
    SegGs:  [0x00000000]
    SegFs:  [0x0000003B]
    SegEs:  [0x00000023]
    SegDs:  [0x00000023]
    Edi:  [0x099F0020]
    Esi:  [0x00006A62]
    Ebx:  [0x08BD5680]
    Edx:  [0x00000001]
    Ecx:  [0x01734000]
    Eax:  [0x05CD6A63]
    Ebp:  [0x03B0F9C4]
    Eip:  [0x6FC4500A] memcpy + 90/880
    SegCs:  [0x0000001B]
    EFlags:  [0x00010212]
    Esp:  [0x03B0F9BC]
    SegSs:  [0x00000023]

 OS: Windows
 Arch: i386

    Frame  0 @[0x03B0F9C4]:  [0x6FC80475] memcpy_s + 72/123
    Frame  1 @[0x03B0F9E0]:  [0x67DA1201]
           std::char_traits<char>::_Copy_s + 21/29
    Frame  2 @[0x03B0F9F8]:  [0x67DA394D]
           std::allocator<char>>::assign + 126/146
    Frame  3 @[0x03B0FA1C]:  [0x67DA5E45]
           std::allocator<char> >::operator= + 13/16
    Frame  4 @[0x05CD287C]:  [0x00006A62] ?
    Frame  5 @[0x0064656B]: (Frame below stack)

 Crash dump written to: C:\Program Files\Splunk\var\log\splunk\C__Program

XXXXXXXXXXX /6.1 Service Pack 1
Threads running: 36
argv: [Splunkd -p 8089]

Further analysis showed that the crash is indeed triggered by an incorrect
source address in a fastcopy_I call. It is unclear where this address comes
from, though and why the crash only happens after a certain amount of


Denial of service of splunkd (and possibly the Splunk web-interface,
depending on configuration) until splunkd is restarted.


This issue has been fixed in Splunk 4.3.5 and 5.0.

Alexander Klink, n.runs AG (discovery)
Moritz Jodeit, n.runs AG (further analysis) 
This advisory and upcoming advisories:
About n.runs:
n.runs AG is a vendor-independent consulting company specializing in the
areas of: IT Infrastructure, IT Security and IT Business Consulting.

Copyright Notice:
Unaltered electronic reproduction of this advisory is permitted. For all
other reproduction or publication, in printing or otherwise, contact for permission. Use of the advisory constitutes
acceptance for use in an "as is" condition. All warranties are excluded.
In no event shall n.runs be liable for any damages whatsoever including
direct, indirect, incidental, consequential, loss of business profits or
special damages, even if n.runs has been advised of the possibility of such
Copyright 2012 n.runs AG. All rights reserved. Terms of use apply.


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