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Security Bulletin: IBM HTTP Server CPU utilization (CVE-2014-0963)

Security Bulletin


IBM HTTP Server is affected by a problem related to the SSL implementation which, under very specific conditions, can cause CPU utilization to rapidly increase.

Vulnerability Details

CVE ID: CVE-2014-0963

IBM HTTP Server is affected by a problem with the handling of certain SSL messages. The TLS implementation can, under very specific conditions, cause CPU utilization to rapidly increase. The situation occurs only in a certain error case that causes a single thread to begin looping. If this happens multiple times, more threads will begin to loop and an increase in CPU utilization will be seen. This increase could ultimately result in CPU exhaustion and unresponsiveness of the IBM HTTP Server and other software running on the affected system.

This issue can affect the availability of the system, but does not impact system confidentiality or integrity. This vulnerability can be remotely exploited, authentication is not required and the exploit is moderately complex.

To determine if your systems are being affected by this issue, you can monitor the CPU utilization for IBM HTTP Server instances, or monitor the mod_mpmstats output written to the ErrorLog.

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

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 7.0
· Version 6.1
· Version 6.0


The recommended solutions is to apply the interim fix, Fix Pack or PTF containing APAR PI17025 for each named product as soon as practical

For affected IBM HTTP Server for WebSphere Application Server:

For V8.5.0.0 through Full Profile:

· Apply Interim Fix PI17025


· Apply Fix Pack or later.

For V8.0 through

· Apply Interim Fix PI17025


· Apply Fix Pack or later.

For V7.0.0.0 through

· Apply Interim Fix PI17025


· Apply Fix Pack or later.

For V6.1.0.0 through

· Apply Interim Fix PI17025

For V6.0.0.0 through

· Apply Interim Fix PI17025

Workarounds and Mitigations

Use any of these workarounds:

  • For Any Release:
    • Disable mod_reqtimeout by commenting out both the line beginning with “LoadModule reqtimeout_module...” in httpd.conf and any line beginning with “RequestReadTimeout”. Note: This is not intuitive, but CVE-2014-0963 does not manifest in IBM HTTP Server without mod_reqtimeout also loaded.
    • Configure very short thresholds with mod_reqtimeout, which shortens the amount of time a thread can be tied up by CVE-2014-0963. See the RequestReadTimeout directive.
  • Monitor CPU utilization of your IBM HTTP Server instances. If utilization becomes abnormally high, stop and restart the affected instance.
  • Monitor mod_mpmstats output for unusual build-up of threads with active module “mod_ibm_ssl"

Get Notified about Future Security Bulletins

Important Note

IBM strongly suggests that all System z customers be subscribed to the System z Security Portal to receive the latest critical System z security and integrity service. If you are not subscribed, see the instructions on the System z Security web site. Security and integrity APARs and associated fixes will be posted to this portal. IBM suggests reviewing the CVSS scores and applying all security or integrity fixes as soon as possible to minimize any potential risk.



Change History

15 May 2014: original document published

*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