CVE-2009-0692: DHCP Stack Overflow in 'dhclient' script_write_params()

ISC dhclient has a stack overflow vulnerability which makes it theoretically possible for a rogue DHCP server to execute arbitrary commands as root on the affected system through stack return subversion.

CVE: 

CVE-2009-0692  

Posting date: 

14 Jul 2009

Program Impacted: 

DHCP

Versions affected: 

DHCP 4.1 (all versions), 4.0 (all versions), 3.1 (all versions), 3.0 (all versions), 2.0 (all versions)

Severity: 

High

Exploitable: 

Remotely

Description:

While generating a subnet number from the server-supplied leased address and subnet-mask 'dhclient' copies the information into a field without verifying if the length of the information exceeds the length of the field.

Theoretically this allows a rogue DHCP server to execute arbitrary
commands as root on the affected system through stack return subversion.

This attack has little to no risk for a client situated on a network that is well defended, whereas clients that are roaming to potentially hostile or ad-hoc networks can see this attack to pose a severe threat.

Factors complicating any attack would be:

1.The attacker would need to generate messages the client views as authentic.

2.The attacker would then need to develop their attack within a limited packet size.

Workarounds:

There is no known workaround, you must install the patches listed below to protect the DHCP client.

Active exploits:

None known at this time

Solution:  

                Upgrade to 4.1.0p1, 4.0.1p1, or 3.1.2p1

There are no fixes planned for DHCP 3.0 or DHCP 2.0, as those release trains have reached End-Of-Life.

Acknowledgements:  

Credit: Mandriva Linux Engineering Team and for discovering and reporting the software flaw.

Related Documents:

If you'd like more information on our Forum or product support please visit www.isc.org/support.

Do you still have questions?   Questions regarding this advisory should go to security-officer@isc.org

Note: ISC patches only currently supported versions. When possible we indicate EOL versions affected.

ISC Security Vulnerability Disclosure Policy:   Details of our current security advisory policy and practice can be found here: https://www.isc.org/security-vulnerability-disclosure-policy

This Knowledge Base article https://kb.isc.org/article/AA-00962 is the complete and official security advisory document.

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