Security Bulletin
Summary
The RC4 “Bar Mitzvah” Attack for SSL/TLS affects Rational Developer for System z.
Vulnerability Details
CVEID: CVE-2015-2808
DESCRIPTION: The RC4 algorithm, as used in the TLS protocol and SSL protocol, could allow a remote attacker to obtain sensitive information. An attacker could exploit this vulnerability to remotely expose account credentials without requiring an active man-in-the-middle session. Successful exploitation could allow an attacker to retrieve credit card data or other sensitive information. This vulnerability is commonly referred to as "Bar Mitzvah Attack".
CVSS Base Score: 5
CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/101851 for the current score
CVSS Environmental Score*: Undefined
CVSS Vector: (AV:N/AC:L/Au:N/C:P/I:N/A:N)
Affected Products and Versions
Rational Developer for System z, versions 8.0.3.x, 8.5.x, 9.0.x and 9.1.x
Workarounds and Mitigations
By default Rational Developer for System z relies on System SSL defaults for active cipher suites, and by default, System SSL enables the RC4 cipher suites for SSLv3 and all TLS versions. Note that usage of SSLv3 is not advised due to another vulnerability commonly referred to as "POODLE vulnerability".
The RC4 ciphers in TLS are:
- TLS_RSA_WITH_RC4_40_MD5 ("03" or "0003")
- TLS_RSA_WITH_RC4_128_MD5 ("04" or "0004")
- TLS_RSA_WITH_RC4_128_MD5 ("05" or "0005")
- TLS_ECDH_ECDSA_WITH_RC4_128_SHA ("C002")
- TLS_ECDHE_ECDSA_WITH_RC4_128_SHA ("C007")
- TLS_ECDH_RSA_WITH_RC4_128_SHA ("C00C")
- TLS_ECDHE_RSA_WITH_RC4_128_SHA ("C011")
You can explicitly disable the usage of the RC4 ciphers by adding the GSK_V3_CIPHER_SPECS environment variable, ensuring that the environment variable character string does not include ciphers "03", "04", or "05".
If environment variable GSK_V3_CIPHERS is set to GSK_V3_CIPHERS_CHAR4 (this must be done explicitly), you can explicitly disable the usage of the RC4 ciphers by adding the GSK_V3_CIPHER_SPECS_EXPANDED environment variable, ensuring that the environment variable character string does not include ciphers "0003", "0004", "0005", "C002", "C007", "C00C", or "C011".
Rational Developer for System z has two components that utilize System SSL:
- RSE, which is used when a client connects to the host. You must specify the GSK_V3_CIPHER_SPECS environment variable in rsed.envvars, by default located in /etc/rdz.
- Debug Manager, by means of an AT-TLS policy. You must create a file holding the GSK_V3_CIPHER_SPECS environment variable and reference it via the Envfile keyword in the TTLSGroupAdvancedParms section.
You should verify applying this configuration change does not cause any compatibility issues. Not disabling the RC4 stream cipher will expose yourself to the attack described above. IBM recommends that you review your entire environment to identify other areas where you have enabled the RC4 stream cipher and take appropriate mitigation and remediation actions.
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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.
References
*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.
Disclaimer
Review the IBM security bulletin disclaimer and definitions regarding your responsibilities for assessing potential impact of security vulnerabilities to your environment.
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Document Information
Modified date:
27 October 2020
UID
swg21701906