Now Available DHCP 4.2.3-P1 and DHCP 4.1-ESV-R4 Notice: ISC DHCP Security Advisory 7 Dec CVE-2011-4539
Susan Graves
sgraves at isc.org
Wed Dec 7 21:32:42 UTC 2011
The Release notes for 4.2.3-P1 is here:
https://deepthought.isc.org/article/AA-00565
for 4.1-ESV-R4 is here: https://deepthought.isc.org/article/AA-00566
------------------------------------
Title: DHCP Regular Expressions Segfault
Summary: Segmentation fault from dhcpd while processing an evaluated
regular expression
CVE: CVE-2011-4539
Document Version: 1.2
Document url: https://www.isc.org/software/bind/advisories/cve-2011-4539
Posting date: 30 November 2011
Program Impacted: DHCP
Versions affected: 4.0.x and higher, including all EOL versions
back to 4.0, 4.1-ESV, and 4.2.x
Severity: Medium
Exploitable: Remotely
Description:
A bug exists which allows an attacker who is able to send DHCP
Request packets, either directly or through a relay, to remotely
crash an ISC DHCP server if that server is configured to evaluate
expressions using a regular expression (i.e. uses the "~=" or "~~"
comparison operators.) Further details are being withheld to allow
administrators of affected systems time to patch. You are potentially
vulnerable if you use regular expression comparison operators in
your dhcpd.conf
CVSS Score: 6.1
CVSS Equation: AV:N/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:N/AC:L/Au:N/C:N/I:N/A:C)
Workarounds:
This bug cannot be triggered if you are not using regular expressions
in your configuration file.
Solution:
Upgrade to 4.1-ESV-R4 or 4.2.3-P1
Download patched versions from the following location:
http://www.isc.org/software/dhcp
Exploit Status: No known active exploits
Acknowledgment:
Thank you to BlueCat Networks for finding and testing the issue.
Document Revision History
1.0 30 November 2011 - Phase I notified
1.1 6 December 2011 - Phase II & III notified
1.2 7 December 2011 - Public Release
Document URL: to be posted with public release
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
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