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Security Bulletin: Potential Denial of service vulnerability in IBM HTTP Server (CVE-2013-6329)

Security Bulletin


A potential denial of service vulnerability in SSL handshake processing in IBM HTTP Server (IHS).

Vulnerability Details

CVEID: CVE-2013-6329
Description: Potential denial of service in SSL handshake processing.
CVSS Base Score: 7.1
CVSS Temporal Score: See for the current score
CVSS Environmental Score*: Undefined
CVSS Vector: (AV:N/AC:M/Au:N/C:N/I:N/A:C)

Affected Products and Versions

VERSIONS AFFECTED: This problem affects the IBM HTTP Server component in all editions of WebSphere Application Server and bundling products:
· Version 8.5.5
· Version 8.5
· Version 8
· Version 7
· Version 6.1


The recommended solution is to apply the Fix Pack or PTF for each named product as soon as practical

Fix:Apply a Fix Pack or PTF containing APAR PI05309, as noted below:

For affected IBM HTTP Server for WebSphere Application Server:

For V8.5.0.0 through Full Profile:

  • Apply Fix Pack or later.

For V8.0 through
  • Apply Fix Pack or later.

For V7.0.0.0 through
Due to a publishing issue with PI05309 for Version 7 only, apply PI09443 which supercedes the fix for PI05309 --OR--
  • Apply Fix Pack or later.

For V6.1.0.0 through

Workarounds and Mitigations

Disabling the SSLv3 Session cache will circumvent this issue, but may lead to higher CPU usage. To use the circumvention:

For Windows platforms, do one of the following:

  • Any Release:
    • Set the system wide environment variable 'GSK_V3_SIDCACHE_SIZE=0"
    • Restart the system

  • For IBM HTTP Server Version or later:
    • Set the following directive everywhere you use the 'SSLEnable' directive:
      • SSLAttributeSet 305 0 NUMERIC

For Other platforms, do one of the following:
  • Any Release:
    • Export the native environment variable 'GSK_V3_SIDCACHE_SIZE=0' in '$IHSROOT/bin/envvars'
    • Perform a full stop and start of the server.
    • Set "SSLCacheDisable" at the bottom of httpd.conf

  • For IHS Version or later:
    • Set the following directive everywhere you use the 'SSLEnable' directive:
      • SSLAttributeSet 305 0 NUMERIC
    • Set "SSLCacheDisable" at the bottom of httpd.conf

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Change History

17 December 2013: original version published
14 February 2014: updated to supercede PI05309 for Version 7

*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.


According to the Forum of Incident Response and Security Teams (FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry open standard designed to convey vulnerability severity and help to determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES ""AS IS"" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY.

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Document Information

Modified date:
15 June 2018