Pierluigi Paganini January 17, 2018

The Internet Systems Consortium (ISC) has issued security updates for BIND to address a high severity vulnerability that could cause DNS servers crash.

The Internet Systems Consortium (ISC) has rolled out security updates for BIND to address a high severity vulnerability that could be remotely exploited to crash DNS servers.

The flaw discovered by Jayachandran Palanisamy of Cygate AB and tracked as CVE-2017-3145, is caused by a use-after-free bug that can lead to an assertion failure and crash of the BIND name server (named) process.

“BIND was improperly sequencing cleanup operations on upstream recursion fetch contexts, leading in some cases to a use-after-free error that can trigger an assertion failure and crash in named.” reads the security advisory published by ISC.

According to the ISC there is no evidence that the flaw has been exploited in attacks in the wild, but the ISC states that many crashes caused by the bug have been reported by “multiple parties.”

The issue impacted systems that operate as DNSSEC validating resolvers, the experts suggest to temporarily disable DNSSEC validation as a workaround.

“While this bug has existed in BIND since 9.0.0, there are no known code paths leading to it in ISC releases prior to those containing the fix for CVE-2017-3137.  Thus while all instances of BIND ought to be patched, only ISC versions [9.9.9-P8 to 9.9.11, 9.10.4-P8 to 9.10.6, 9.11.0-P5 to 9.11.2, 9.9.9-S10 to 9.9.11-S1, 9.10.5-S1 to 9.10.6-S1, and 9.12.0a1 to 9.12.0rc1] acting as DNSSEC validating resolvers are currently known to crash due to this bug.  The known crash is an assertion failure in netaddr.c.” continues the advisory.

The ISC also disclosed a medium severity DHCP flaw tracked as CVE-2017-3144  that affect versions 4.1.0 to 4.1-ESV-R15, 4.2.0 to 4.2.8, and 4.3.0 to 4.3.6.

“A vulnerability stemming from failure to properly clean up closed OMAPI connections can lead to exhaustion of the pool of socket descriptors available to the DHCP server. ” reads the ISC advisory.

“By intentionally exploiting this vulnerability an attacker who is permitted to establish connections to the OMAPI control port can exhaust the pool of socket descriptors available to the DHCP server. Once exhausted, the server will not accept additional connections, potentially denying access to legitimate connections from the server operator. While the server will continue to receive and service DHCP client requests, the operator can be blocked from the ability to use OMAPI to control server state, add new lease reservations, etc.,”

ISC has already developed a patch that will be rolled out in the future DHCP releases, as a workaround it is possible to disallow access to the OMAPI control port from unauthorized clients.

Pierluigi Paganini

(Security Affairs –BIND, hacking)

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