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AUSCERT External Security Bulletin Redistribution
ESA-2012-029: RSA BSAFEÂ® SSL-C Multiple Vulnerabilities
12 September 2012
AusCERT Security Bulletin Summary
Product: RSA BSAFE SSL-C
Operating System: Windows
Impact/Access: Access Privileged Data -- Remote with User Interaction
Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2012-2131 CVE-2012-2110 CVE-2011-3389
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ESA-2012-029: RSA BSAFEÂ® SSL-C Multiple Vulnerabilities
EMC Identifier: ESA-2012-029
CVE Identifier: CVE-2011-3389, CVE-2012-2110, CVE-2012-2131
Severity Rating: See below for scores for individual issues
All versions of RSA BSAFE SSL-C prior to 2.8.6, all platforms
RSA BSAFE SSL-C 2.8.6
RSA BSAFE SSL-C 2.8.6 contains fixes designed to [prevent] BEAST attacks
(CVE-2011-3389) and buffer overflow vulnerability
This release includes fixes for the following vulnerabilities:
1.BEAST (Browser Exploit Against SSL/TLS) attack (CVE-2011-3389
>There is a known vulnerability in SSLv3 and TLS v1.0 to do with how the
Initialization Vector (IV) is generated. For symmetric key algorithms in CBC
mode, the IV for the first record is generated using keys and secrets set
during the SSL or TLS handshake. All subsequent records are encrypted using the
ciphertext block from the previous record as the IV. With symmetric key
encryption in CBC mode, plain text encrypted with the same IV and key generates
the same cipher text, which is why having a variable IV is important.
The BEAST exploit uses this SSLv3 and TLS v1.0 vulnerability by allowing an
attacker to observe the last ciphertext block, which is the IV, then replace
this with an IV of their choice, inject some of their own plain text data, and
when this new IV is used to encrypt the data, the attacker can guess the plain
text data one byte at a time.
CVSSv2 Base Score: 4.3 (AV:N/AC:M/Au:N/C:P/I:N/A:N)
2.Buffer overflow vulnerability (CVE-2012-2110/CVE-2012-2131)
SSL-C contains code that does not properly interpret integer data, which could
allow buffer overflow attacks using crafted DER (Distinguished Encoding Rules)
data, such as in X.509 certificate or an RSA asymmetric key.
CVSSv2 Base Score: 7.5 (AV:N/AC:L/Au:N/C:P/I:P/A:P)
For BEAST (Browser Exploit Against SSL/TLS) attack:
The best way to help prevent this attack is to use TLS v1.1. The vulnerability
to do with IV generation was fixed in TLS v1.1 (released in 2006) so
implementations using only TLS v1.1 are engineered to be secure against the
BEAST exploit. However, support for this higher level protocol is limited to a
smaller number of applications, so supporting only TLS v1.1 might cause
A second solution is to limit the negotiated cipher suites to exclude those
that do not require symmetric key algorithms in CBC mode. However, this
substantially restricts the number of cipher suites that can be negotiated.
That is, only cipher suites with NULL encryption or cipher suites with
streaming encryption algorithms (the RC4 algorithm) could be negotiated.
In RSA BSAFE SSL-C 2.8.6, the BEAST exploit is prevented by introducing some
unknown data into the encryption scheme, prior to the attackers inserted plain
text data. This is done as follows:
1.The first plain text block to be encrypted is split into two blocks. The
first block contains the first byte of the data, the second block contains the
2.A MAC is generated from the one byte of data, the MAC key, and an increasing
counter. This MAC is included in the first block.
3.The one byte of data, along with the MAC, is encrypted and becomes the IV for
the next block. Because the IV is now essentially random data, it is impossible
for an attacker to predict it and replace it with one of their own.
To manage this first block splitting in RSA BSAFE SSL-C 2.8.6, either for an
SSL context or SSL object, call R_SSL_CTX_set_options() or R_SSL_set_options()
respectively, with the SSL_OP_SPLIT_FIRST_FRAGMENT identifier, this option is
enabled by default.
For more information about these functions and identifiers, see the RSA BSAFE
SSL-C 2.8.6 API Reference Guide.
For Buffer Overflow vulnerability:
RSA strongly recommends that RSA BSAFE SSL-C customers upgrade to RSA BSAFE
SSL-C 2.8.6 that contains upgrades designed to resolve this issue.
For an explanation of Severity Ratings, refer to the Knowledge Base Article,
Security Advisories Severity Rating at
recommends all customers take into account both the base score and any relevant
temporal and environmental scores which may impact the potential severity
associated with particular security vulnerability.
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