Red Hat Bugzilla – Bug 761265
CVE-2011-4539 dhcp: DoS due to processing certain regular expressions
Last modified: 2012-01-02 18:05:17 EST
It was reported  that ISC dhcpd suffered from a bug related to processing an evaluated regular expression. If an attacker were able to send a DHCP Request packet, either directly or through a relay, they could remotely crash dhcpd if that server was configured to evaluate expressions using a regular expression (such as "~=" or "~~" comparison operators). No further details have been released as of yet.
Upstream indicates that 4.0.x and higher, including all EOL versions back to 4.0, 4.1-ESV, and 4.2.x, are affected and is corrected in 4.1-ESV-R4 and 4.2.3-P1.
This flaw cannot be triggered if regular expressions are not used in the server's configuration files.
Created attachment 542241 [details]
diff from 4.2.3 and 4.2.3-P1
Diff from 4.2.3 and 4.2.3-P1 with the following changelog comments:
Changes since 4.2.3
! Add a check for a null pointer before calling the regexec function.
Without out this check we could, under some circumstances, pass
a null pointer to the regexec function causing it to segfault.
Thanks to a report from BlueCat Networks.
Created dhcp tracking bugs for this issue
Affects: fedora-all [bug 765681]
This issue does not affect the version of dhcp package as shipped with Red Hat Enterprise Linux 4 and 5.
This issue affects the version of dhcp package as shipped with Red Hat Enterprise Linux 6.
This issue did not affect the versions of dhcp as shipped with Red Hat Enterprise Linux 4 and 5.
This issue has been addressed in following products:
Red Hat Enterprise Linux 6
Via RHSA-2011:1819 https://rhn.redhat.com/errata/RHSA-2011-1819.html
dhcp-4.2.3-4.P1.fc16 has been pushed to the Fedora 16 stable repository. If problems still persist, please make note of it in this bug report.
dhcp-4.2.1-14.P1.fc15 has been pushed to the Fedora 15 stable repository. If problems still persist, please make note of it in this bug report.