n.runs AG
http://www.nruns.com/                              security(at)nruns.com
n.runs-SA-2012.003                                           02-Nov-2012
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Vendors:            Splunk Inc., http://www.splunk.com
Product:            Splunk 4.3.x (+ possibly earlier versions)
Vulnerability:      Unauth. remote denial of service against splunkweb
Tracking IDs:       CVE-2012-1150
                    SPL-53249
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Vendor communication:
2012/09/03 Reported the issue via Splunk's website
2012/09/04 Splunk responds and assigns tracking ID, plans fix for 5.0.
                       Replacing the Python version in a maintenance release
(4.3.x)
         was considered too risky.
2012/10/25 Splunk informs us that 5.0 will be available on November 1st.
2012/10/29 Splunk 5.0 is released.
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Overview:

Splunkweb uses Python 2.7.2, which suffers from a vulnerability which allows
an
attacker to produce hash collisions for the hash table string hashing
function.
This leads to an O(n^2) complexity when inserting n keys (see
http://bugs.python.org/issue13703).

Description:

An attacker can abuse this vulnerability by sending a POST request to
Splunkweb
(for example to the login form endpoint) with colliding keys. Even a
moderate
amount of POST data leads to a 100% CPU usage for the splunkweb process.

Impact:

Denial of service (CPU exhaustion) against the Splunk server.

Fixes:

This issue has been fixed in Splunk 5.0 by updating the Python version
to 2.7.3 and enabling hash randomization.  

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Credits:
Alexander Klink, n.runs AG (discovery)
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References:
This advisory and upcoming advisories:
http://www.nruns.com/security_advisory.php
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About n.runs:
n.runs AG is a vendor-independent consulting company specialising in the
areas of: IT Infrastructure, IT Security and IT Business Consulting.

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