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Crypt::CBC: Insecure initialization vector


1.  Gentoo Linux Security Advisory

Version Information

Advisory Reference GLSA 200603-15 / crypt-cbc
Release Date March 17, 2006
Latest Revision March 17, 2006: 01
Impact low
Exploitable remote
Package Vulnerable versions Unaffected versions Architecture(s)
dev-perl/crypt-cbc < 2.17 >= 2.17 All supported architectures

Related bugreports: #126048


Crypt::CBC uses an insecure initialization vector, potentially resulting in a weaker encryption.

2.  Impact Information


Crypt::CBC is a Perl module to encrypt data using cipher block chaining (CBC).


Lincoln Stein discovered that Crypt::CBC fails to handle 16 bytes long initializiation vectors correctly when running in the RandomIV mode, resulting in a weaker encryption because the second part of every block will always be encrypted with zeros if the blocksize of the cipher is greater than 8 bytes.


An attacker could exploit weak ciphertext produced by Crypt::CBC to bypass certain security restrictions or to gain access to sensitive data.

3.  Resolution Information


There is no known workaround at this time.


All Crypt::CBC users should upgrade to the latest available version:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-perl/crypt-cbc-2.17"

4.  References


Page updated March 17, 2006

Summary: This is a Gentoo Linux Security Advisory

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