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Family: Ubuntu Local Security Checks --> Category: infos

USN170-1 : gnupg vulnerability Vulnerability Scan

Vulnerability Scan Summary
gnupg vulnerability

Detailed Explanation for this Vulnerability Test

Synopsis :

The remote package "gnupg" is missing a security patch.

Description :

Serge Mister and Robert Zuccherato discovered a weakness of the
symmetrical encryption algorithm of gnupg. When decrypting a message,
gnupg uses a feature called "quick scan"
this can quickly check
whether the key that is used for decryption is (probably) the right
one, so that wrong keys can be acertaind quickly without decrypting
the whole message.

A failure of the quick scan will be acertaind much faster than a
successful one. Mister/Zuccherato demonstrated that this timing
difference can be exploited to an attack which allows a possible hacker to
decrypt parts of an encrypted message if an "oracle" is available, i.
e. an automatic system that receives random encrypted messages from
the attacker and answers whether it passes the quick scan check.

However, since the attack requires a huge amount of oracle answers
(about 32.000 for every 16 bytes of ciphertext), this attack is mostly
theoretical. It does not have any impact on human operation of gnupg
and is not believed to be exploitable in practice.


Solution :

Upgrade to :
- gnupg-1.2.5-3ubuntu5.1 (Ubuntu 5.04)

Threat Level: High

Click HERE for more information and discussions on this network vulnerability scan.


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