PowerDNS Security Advisory 2017-01 for dnsdist: Crafted backend responses can cause a denial of service ======================================================================================================= - CVE: CVE-2016-7069 - Date: 2017-08-21 - Credit: Guido Vranken - Affects: dnsdist up to and including 1.2.0 on 32-bit systems - Not affected: dnsdist 1.2.0, dnsdist on 64-bit (all versions) - Severity: Low - Impact: Degraded service or Denial of service - Exploit: This issue can be triggered by sending specially crafted response packets from a backend - Risk of system compromise: No - Solution: Upgrade to a non-affected version - Workaround: Disable EDNS Client Subnet addition An issue has been found in dnsdist in the way EDNS0 OPT records are handled when parsing responses from a backend. When dnsdist is configured to add EDNS Client Subnet to a query, the response may contain an EDNS0 OPT record that has to be removed before forwarding the response to the initial client. On a 32-bit system, the pointer arithmetic used when parsing the received response to remove that record might trigger an undefined behavior leading to a crash. dnsdist up to and including 1.1.0 is affected on 32-bit systems. dnsdist 1.2.0 is not affected, dnsdist on 64-bit systems is not affected. For those unable to upgrade to a new version, a minimal patch is `available for 1.1.0 `__ We would like to thank Guido Vranken for finding and subsequently reporting this issue.