- 26 Sep 2014
- 2 Minutes to read
CVE-2011-0997: dhclient Does Not Strip or Escape Shell Meta-characters
- Updated on 26 Sep 2014
- 2 Minutes to read
Fixes for ISC this dhclient vulnerability do not protect against September 2014 bash flaws
Despite reports from some sources to the contrary, ISC has determined that the changes made in this fix do not prevent exploitation of the September 2014 bash vulnerabilities CVE-2014-6271 and CVE-2014-7169
DHCP: dhclient does not strip or escape shell meta-characters
dhclient doesn't strip or escape certain shell meta-characters in dhcpd responses, allowing a rogue server or party with with escalated privileges on the server to cause remote code execution on the client.
05 Apr 2011
ISC dhclient did not strip or escape certain shell meta-characters in responses from the dhcp server (like hostname) before passing the responses on to dhclient-script. Depending on the script and OS, this can result in execution of exploit code on the client.
CVSS Score : 6.8 (AV:A/AC:L/Au:N/C:P/I:N/A:C) For more information on CVSS scores, visit http://nvd.nist.gov/cvss.cfm?calculator&adv&version=2
On SUSE systems, it is possible to disable hostname update by setting DHCLIENT_SET_HOSTNAME="no" in /etc/sysconfig/network/dhcp. Other systems may add following line to dhclient-script at the beginning of the set_hostname() function:
In environments where filters/acls can be put into place to limit clients to accessing only legitimate dhcp servers, this will protect clients from rogue dhcp servers deliberately trying to exploit this bug. However, this will not protect from compromised servers.
None known at this time.
Upgrade to 3.1-ESV-R1, 4.1-ESV-R2 or 4.2.1-P1. https://www.isc.org/downloads/all
No patch is available for 4.0.x as it is EOL. Anyone running 4.1.x should upgrade to 4.1-ESV-R2.
Acknowledgments: Sebastian Krahmer and Marius Tomaschewski, SUSE Security Team
Revisions: Mar29-Updated CVSS score Apr6-Corrected workaround
Do you have Questions? Questions regarding this advisory should go to email@example.com.
This security advisory is a copy of the official document located on our website: https://www.isc.org/software/dhcp/advisories/cve-2011-0997
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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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