ISC Security Advisory: An Error in the Handling of Malformed Client Identifiers can Cause a Denial-of-Service Condition in Affected Servers

Cathy Almond cathya at isc.org
Tue Jul 24 17:51:12 UTC 2012


Note: This email advisory is provided for your information. The most up
to date advisory information will always be at:
https://kb.isc.org/article/AA-00712
please use this URL for the most up to date advisory information.

Title: An error in the handling of malformed client identifiers can
cause a denial-of-service condition in affected servers.

CVE: CVE-2012-3571
Document Version:          2.0
Posting date: 24 Jul 2012
Program Impacted: DHCP
Versions affected: All versions of 4.2 (including 4.2.x-Px) to 4.2.4;
4.1-ESV through 4.1-ESV-R5; 4.1.2, 4.1.2-P1
Severity: High
Exploitable: Locally - From adjacent networks

Description:

An error in the handling of malformed client identifiers can cause a
DHCP server running affected versions (see "Impact") to enter a state
where further client requests are not processed and the server process
loops endlessly, consuming all available CPU cycles.

Under normal circumstances this condition should not be triggered, but a
non-conforming or malicious client could deliberately trigger it in a
vulnerable server. In order to exploit this condition an attacker must
be able to send requests to the DHCP server .

Impact:

Causes the server process to loop endlessly, resulting in a denial of
service.  NOTE: ISC DHCP 3.0.x and ISC DHCP 4.0.x are EOL and have not
been tested for this vulnerability. Versions of ISC DHCP that are
vulnerable to CVE-2010-2156 (including 4.1.0 through 4.1.1-P1) can be
expected to terminate unexpectedly instead of looping endlessly.

CVSS Score: 6.1

CVSS Equation:  (AV:A/AC:L/Au:N/C:N/I:N/A:C)
For more information on the Common Vulnerability Scoring System and to
obtain your specific environmental score please visit
http://nvd.nist.gov/cvss.cfm?calculator&adv&version=2&vector=(AV:A/AC:L/Au:N/C:N/I:N/A:C)
Workarounds:

None.
Active exploits:

None known at this time.

Solution:

Upgrade affected systems to DHCP 4.1-ESV-R6 or DHCP 4.2.4-P1

DHCP 4.2.4-P1 is available from www.isc.org/downloads/all

DHCP 4.1-ESV-R6 is available from www.isc.org/downloads/all

Acknowledgment:
Markus Hietava of Codenomicon CROSS project for finding the
vulnerability, and CERT-FI for vulnerability coordination.

Document Revision History:

    1.0 - 03 July 2012 Phase I notified
    1.1 - 13 July 2012 HOLD notice sent to Phase 1 regarding new CVE
being added and new public release date
    1.2 - 23 July 2012 Phase 2 & 3 notified
    2.0 - 24 July 2012 Phase 4-Public released

References:

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

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

    German Translation: https://kb.isc.org/article/AA-00739
    Spanish Translation: https://kb.isc.org/article/AA-00747
    Japanese Translation: https://kb.isc.org/article/AA-00755

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