CVE-2017-3144: Failure to properly clean up closed OMAPI connections can exhaust available sockets
mcnally at isc.org
Tue Jan 16 21:14:27 UTC 2018
Document Version: 2.0
Posting date: 16 Jan 2018
Program Impacted: DHCP
Versions affected: 4.1.0 to 4.1-ESV-R15, 4.2.0 to 4.2.8, 4.3.0 to 4.3.6.
Older versions may also be affected but are well beyond
their end-of-life (EOL). Releases prior to 4.1.0 have
not been tested.
Exploitable: Remotely (if attackers are permitted access to a
server's OMAPI control port)
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.
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
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
CVSS Score: 5.3
CVSS Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
For more information on the Common Vulnerability Scoring System and
to obtain your specific environmental score please visit:
The recommended remedy is to disallow access to the OMAPI control
port from unauthorized clients (in accordance with best practices
for server operation).
ISC has written a patch which properly cleans up closed socket
connections and will include it in future maintenance releases
of ISC DHCP. The patch is also available upon request (to
security-officer at isc.org) to parties who want to incorporate it
into their own code before the next ISC maintenance releases.
However, we do not plan to issue a special security patch release
of DHCP to address this particular issue because we have concluded
that the workaround of denying OMAPI connections from unauthorized
client addresses should be sufficient in almost all cases and
is a recommended best practice for server operation.
Document Revision History:
1.0 Advance notification, 08 January 2018
2.0 Public disclosure, 16 January 2018
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ISC patches only currently supported versions. When possible we
indicate EOL versions affected. (For current information on
which versions are actively supported, please see
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This Knowledge Base article https://kb.isc.org/article/AA-01541 is
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