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CERT Coordination Center


Cisco ASA and FTD SIP Inspection denial-of-service vulnerability

Vulnerability Note VU#339704

Original Release Date: 2018-11-01 | Last Revised: 2018-11-05

Overview

Cisco Adaptive Security Appliance (ASA) software and Cisco Firepower Threat Defense (FTD) software fails to properly parse SIP traffic, which can result in a denial-of-service condition on affected devices.

Description

Cisco Adaptive Security Appliance (ASA) software and Cisco Firepower Threat Defense (FTD) software fails to properly parse SIP traffic, which can allow an attacker to trigger high CPU usage, resulting in a denial-of-service condition on affected devices. This vulnerability is exposed if SIP Inspection is enabled on affected devices, which is the default configuration on ASA devices. The Cisco SIP Inspection feature is advertised to "... enforce the sanity of the SIP messages, as well as detect SIP-based attacks."

Impact

By causing an affected Cisco device to parse specially-crafted SIP traffic, a remote, unauthenticated attacker may be able to trigger a denial-of-service condition on affected devices.

Solution

The CERT/CC is currently unaware of a practical solution to this problem. Please consider the following workarounds:

Disable SIP Inspection

According to the Cisco advisory:

    Disabling SIP inspection will completely close the attack vector for this vulnerability. However, it may not be suitable for all customers. In particular, disabling SIP inspection would break SIP connections if either NAT is applied to SIP traffic or if not all ports required for SIP communication are opened via ACL.

    To disable SIP inspection, configure the following:

    Cisco ASA Software and Cisco FTD Software Releases 6.2 and later (in FTD 6.2 and later use Cisco FMC to add the following via FlexConfig policy):

        policy-map global_policy
         class inspection_default
          no inspect sip

    Cisco FTD Software Releases prior to 6.2:

    configure inspection sip disable

Vendor Information

339704
Expand all

Cisco

Updated:  November 01, 2018

Status

  Affected

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Vendor References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco -sa-20181031-asaftd-sip-dos

Addendum

There are no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.


CVSS Metrics

Group Score Vector
Base 7.8 AV:N/AC:L/Au:N/C:N/I:N/A:C
Temporal 7.4 E:H/RL:W/RC:C
Environmental 5.5 CDP:ND/TD:M/CR:ND/IR:ND/AR:ND

References

Credit

This vulnerability was publicly reported by Cisco.

This document was written by Will Dormann.

Other Information

CVE IDs: CVE-2018-15454
Date Public: 2018-10-31
Date First Published: 2018-11-01
Date Last Updated: 2018-11-05 19:20 UTC
Document Revision: 25

Sponsored by the Department of Homeland Security Office of Cybersecurity and Communications.