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Age in Days
CVSS Score
Patch within next
Risk Level

3836


10.0

Immediately

Critical

 

This vulnerability is 10 years 6 months and 0 days old there are exploits publicly available for it. The vulnerability itself is over a year old, and with there being exploits publicly available it is highly advisable that this vulnerability is patched immediately.

 

Synopsis

The remote SSH host keys are weak.

 

Vulnerability Description

The remote SSH host key has been generated on a Debian or Ubuntu system which contains a bug in the random number generator of its OpenSSL library.

The problem is due to a Debian packager removing nearly all sources of entropy in the remote version of OpenSSL.

An attacker can easily obtain the private part of the remote key and use this to set up decipher the remote session or set up a man in the middle attack.

On May 13th, 2008 the Debian project announced that Luciano Bello found an interesting vulnerability in the OpenSSL package they were distributing. The bug in question was caused by the removal of the following line of code from md_rand.c

	MD_Update(&m,buf,j);
	[ .. ]
	MD_Update(&m,buf,j); /* purify complains */

These lines were removed because they caused the Valgrind and Purify tools to produce warnings about the use of uninitialized data in any code that was linked to OpenSSL. You can see one such report to the OpenSSL team here. Removing this code has the side effect of crippling the seeding process for the OpenSSL PRNG. Instead of mixing in random data for the initial seed, the only "random" value that was used was the current process ID. On the Linux platform, the default maximum process ID is 32,768, resulting in a very small number of seed values being used for all PRNG operations.

The remote x509 certificate on the remote SSL server has been generated on a Debian or Ubuntu system which contains a bug in the random number generator of its OpenSSL library.

The problem is due to a Debian packager removing nearly all sources of entropy in the remote version of OpenSSL.

An attacker can easily obtain the private part of the remote key and use this to decipher the remote session or set up a man in the middle attack.

 

Solution

Consider all cryptographic material generated on the remote host to be guessable. In particuliar, all SSH, SSL and OpenVPN key material should be re-generated.

 

Further Information

 

CVE References

CVE-2008-0166 NIST | MITRE | CVEDetails

 

Get in touch

Should you have any questions regarding this or any security matter, please do not hesitate to get in touch by emailing the Hedgehog Cyber Operations Team.

Whilst every effort is made to ensure the accuracy and robustness of any information presented, it is not possible for Hedgehog Cyber to test every possible scenario an organisation may face, and Hedgehog Cyber cannot be held liable for any loss or damage which may arise from taking action on any of the contents provided. Hedgehog Cyber strongly advises that all recommendations, solutions and detection methods detailed, are thoroughly reviewed and tested in non-production environments before being considered suitable for production release, in-line with any existing internal change control procedures.