The WebSEAL component in all versions of Tivoli Access Manager for e-business is affected by a problem in which, under very specific conditions, CPU utilization can rapidly increase and not decrease. This issue is related to the SSL implementation in WebSEAL.
The WebSEAL component in all versions of Tivoli Access Manager for e-business is affected by a problem with the handling of certain SSL messages. The TLS implementation in a component of WebSEAL can, under very specific conditions, cause CPU utilization to rapidly increase and not decrease. 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 could ultimately result in CPU exhaustion and unresponsiveness of Access Manager 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 of your WebSEAL instances.
CVSS Base Score: 7.1
CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/92844 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
- All versions of Tivoli Access Manager (TAM) for e-business: 5.1, 6.0, 6.1, 6.1.1
IBM has provided updates containing the fix. Affected systems should be patched immediately. Patches and installation instructions are provided at the URLs listed below.
|TAM for e-business 6.0||IV59660||6.0.0-ISS-TAM-IF0033|
|TAM for e-business 6.1||IV59660||6.1.0-ISS-TAM-IF0014|
|TAM for e-business 6.1.1||IV59660||6.1.1-ISS-TAM-IF0010|
Version 5.1 is no longer supported. IBM recommends upgrading to a fixed, supported version of the product.
Workarounds and Mitigations
There are two methods to mitigate impacts.
Method One: Monitor CPU utilization of your WebSEAL instances. If utilization becomes abnormally high, stop and restart the affected instances.
Method Two) Enable SSLv3 and disable all versions of TLS used by WebSEAL. To do this, perform these steps for every WebSEAL instance in your environment
- In the [ssl] stanza of the WebSEAL instance configuration file, enable SSLv3 by setting the following parameter:
disable-ssl-v3 = no
- In the [ssl] stanza of the WebSEAL instance configuration file, disable all versions of TLS by setting every parameter that starts with "disable-tls" to "yes"
- Restart the WebSEAL instance.
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*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.
16 June 2018