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OpenSSL CBC Plaintext Block Disclosure Vulnerability
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Secunia Advisory:
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SA8101
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Release Date:
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2003-02-20
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Last Update:
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2003-12-05
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Popularity:
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10,422 views
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Critical:
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Less critical
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Impact:
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Exposure of sensitive information
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Where:
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From remote
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Solution Status:
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Vendor Patch
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| Software: | OpenSSL 0.9.x
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| CVE reference: | CVE-2003-0078
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Description:
An information disclosure vulnerability identified in OpenSSL (0.9.6c and newer) can be exploited by a malicious person to gain knowledge of a plaintext block used to encrypt a session.
An attacker, who is able to monitor and manipulate multiple SSL or TLS connections involving a common fixed plaintext block (eg. password), can use a certain attack vector to obtain the complete plaintext block used.
The problem is that MAC (Message Authetication Code) verification is skipped during decryption if a padding error is detected. An attacker can therefore replace some ciphertext blocks with blocks sent by legitimate SSL/TLS parties and record the time until a response is recieved. Depending on the time measured an attacker can distinguish between the two error cases.
The vulnerability is only present in the CBC ciphersuites.
Solution:
Upgrade to OpenSSL 0.9.7a or to OpenSSL 0.9.6i or apply patches.
http://www.openssl.org
Provided and/or discovered by:
Brice Canvel, Alain Hiltgen, Serge Vaudenay and Martin Vuagnoux.
Changelog:
2003-12-05: Added CVE reference.
Original Advisory:
http://www.openssl.org/news/secadv_20030219.txt
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Please note: The information that this Secunia Advisory is based on comes from a third party unless stated otherwise.
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