Asterisk Vulnerabilities

Several vulnerabilities exist in various Asterisk products that can lead to Denial of Service conditions, the bypassing of security restrictions and may allow the compromise of an affected system.

Two of the vulnerabilities are a result of errors that can arise when RTP codecs are processed. If more than 32 RTP payloads are sent a stack-based buffer overflow may occur. In the other case a specially crafted SIP packet can be used to write 0 into certain memory locations. The final vulnerability is a result of problems that exist in SIP channel driver.

Make sure that you have updated to the releases below, as is applicable to your site:

Update to version 1.2.27.
Update to version

Asterisk Business Edition:
Update to version B.2.5.1 and C.1.6.2.

s800i (Asterisk Appliance):
Update to version

Asterisk Appliance Developer Kit:
Fixed in the SVN repository. Please see the vendor’s advisories for details.

SWF Whitepaper and VoIP Vulns

There is a guide available from Adobe on creating secure Flash applications. In the wake of the mid December Adobe Shockwave Flash vulnerabilities, Adobe has released a white paper on “Creating more secure SWF web applications”. This, combined with flash data validation libraries available from Google, allow for a complete solution to any potential vulnerabilities. Developers of Flash animations/movies/applications should take the time to read over this document and see where they could use the data validation libraries within their environment. Security teams should be testing all of their environments Flash applications for any vulnerabilities and coordinate to get these resolved. From what I’ve read, when Adobe makes the second update for these issues available early 2008, the issues will not be completely resolved in already developed Flash applications.

Here’s a link to the article and the validation libraries

Also, it appears a few SIP vendors have had vulnerabilities reported in them today. Avaya is affected by two issues, one in pam and the other in OpenSSH. The issue in pam could allow for the disclosure of sensitive data, or allow the injection of characters into log entries. The issue with OpenSSH could allow arbitrary code execution (race condition) and the discovery of valid usernames. Here’s the original Avaya advisories: and

Asterisk is vulnerable to a Denial of Service when handling the “BYE/Also” transfer method. Exploitation requires that a dialog already be established between the two parties. Asterisk versions prior to 1.4.17 are vulnerable. The issue is fixed in version 1.4.17.