Red Hat Bugzilla – Bug 1495416
CVE-2017-14496 dnsmasq: integer underflow leading to buffer over-read in the EDNS0 code
Last modified: 2017-10-03 16:59:16 EDT
Red Hat Product Security has been made aware of a Denial of Service vulnerability affecting the DNS implementation of dnsmasq.
Acknowledgments: Name: Felix Wilhelm (Google Security Team), Fermin J. Serna (Google Security Team), Gabriel Campana (Google Security Team), Kevin Hamacher (Google Security Team), Ron Bowes (Google Security Team)
Versions of dnsmasq shipped with Red Hat Enterprise Linux 6 and 5 do not include the EDNS0 code which includes this flaw.
Further details from the 2.78 pre-release CHANGELOG: Fix DoS in DNS. Invalid boundary checks in the add_pseudoheader function allows a memcpy call with negative size An attacker which can send malicious DNS queries to dnsmasq can trigger a DoS remotely. dnsmasq is vulnerable only if one of the following option is specified: --add-mac, --add-cpe-id or --add-subnet. CVE-2017-14496 applies. Credit to Felix Wilhelm, Fermin J. Serna, Gabriel Campana and Kevin Hamacher of the Google Security Team for finding this.
Created attachment 1330995 [details] Upstream commit
Relevant memcpy call that could be called with negative (type casted to large positive) size was added in this commit: http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commitdiff;h=5bb88f096363e66ac08e31761f850a1d5aa22244 The first upstream version including this change is 2.76.
External References: https://access.redhat.com/security/vulnerabilities/3199382 https://security.googleblog.com/2017/10/behind-masq-yet-more-dns-and-dhcp.html
Created dnsmasq tracking bugs for this issue: Affects: fedora-all [bug 1497691]
Upstream commit: http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commitdiff;h=897c113fda0886a28a986cc6ba17bb93bd6cb1c7 Google Security Team's repository with test cases: https://github.com/google/security-research-pocs/tree/master/vulnerabilities/dnsmasq
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Via RHSA-2017:2836 https://access.redhat.com/errata/RHSA-2017:2836
Statement: Red Hat OpenStack Platform includes the dnsmasq-utils RPM which does not contain this flaw's affected code-paths; Red Hat OpenStack Platform is therefore listed as not affected. However, because all versions of Red Hat OpenStack Platform are based on Red Hat Enterprise Linux, all Red Hat OpenStack Platform users should absolutely upgrade the dnsmasq RPM from Red Hat Enterprise Linux as a matter of urgency using standard update mechanisms (such as 'yum update' or 'openstack overcloud update').