CVE-2017-3144: Failure to properly clean up closed OMAPI connections can exhaust available sockets

Michael McNally mcnally at isc.org
Tue Jan 16 21:14:27 UTC 2018


CVE:                 CVE-2017-3144
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.
Severity:            Medium
Exploitable:         Remotely (if attackers are permitted access to a
                     server's OMAPI control port)

Description:

   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.

Impact:

   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.

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:
https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Workarounds:

   The recommended remedy is to disallow access to the OMAPI control
   port from unauthorized clients (in accordance with best practices
   for server operation).

Active exploits:

   None known.

Solution:

   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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Note:

   ISC patches only currently supported versions. When possible we
   indicate EOL versions affected.  (For current information on
   which versions are actively supported, please see
   http://www.isc.org/downloads/).

ISC Security Vulnerability Disclosure Policy:

   Details of our current security advisory policy and practice can
   be found here: https://kb.isc.org/article/AA-00861

This Knowledge Base article https://kb.isc.org/article/AA-01541 is
the complete and official security advisory document.

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