OpenBSD PRNG weak security

openbsd-prng-weak-security (40329)

Low Risk

Description:

OpenBSD could provide weaker than expected security, caused by a vulnerability in the pseudo random number generator (PRNG) that uses XOR and "Algorithm X3", where predictable sequence IDs are generated. By observing some consecutive transaction ID values, a remote attacker could exploit this vulnerability to guess the next DNS transaction ID and perform DNS Cache Poisoning.

*CVSS:

Base Score:	4.3
Access Vector:	Network
Access Complexity:	Medium
Authentication:	None
Confidentiality Impact:	None
Integrity Impact:	Partial
Availability Impact:	None
Temporal Score:	3.2
Exploitability:	Unproven
Remediation Level:	Official-Fix
Report Confidence:	Confirmed

Consequences:

Gain Access

Remedy:

Apply the appropriate update for your system. See References.

References:

• OpenBSD Web site: OpenBSD.
• Trusteer Web site: OpenBSD DNS Cache Poisoning and Multiple O/S Predictable IP ID Vulnerability.
• BID-27647: OpenBSD PRNG DNS Cache Poisoning and Predictable IP ID Weakness
• CVE-2008-1146: A certain pseudo-random number generator (PRNG) algorithm that uses XOR and 3-bit random hops (aka Algorithm X3), as used in OpenBSD 2.8 through 4.2, allows remote attackers to guess sensitive values such as DNS transaction IDs by observing a sequence of previously generated values. NOTE: this issue can be leveraged for attacks such as DNS cache poisoning against OpenBSD's modification of BIND.
• SA28819: OpenBSD DNS Server PRNG Transaction ID Vulnerability

Platforms Affected:

• OpenBSD OpenBSD 2.8 - 4.2

Reported:

Feb 06, 2008

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The information within this database may change without notice. Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. In no event shall IBM be held liable for any damages whatsoever arising out of or in connection with the use or spread of this information.

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