#VU32186 Buffer overflow in Asterisk Open Source - CVE-2016-9937

Vulnerability identifier: #VU32186

Vulnerability risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2016-9937

CWE-ID: CWE-119

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Asterisk Open Source
Server applications / Conferencing, Collaboration and VoIP solutions

Vendor: Digium (Linux Support Services)

Description

The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.

An issue was discovered in Asterisk Open Source 13.12.x and 13.13.x before 13.13.1 and 14.x before 14.2.1. If an SDP offer or answer is received with the Opus codec and with the format parameters separated using a space the code responsible for parsing will recursively call itself until it crashes. This occurs as the code does not properly handle spaces separating the parameters. This does NOT require the endpoint to have Opus configured in Asterisk. This also does not require the endpoint to be authenticated. If guest is enabled for chan_sip or anonymous in chan_pjsip an SDP offer or answer is still processed and the crash occurs.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Asterisk Open Source: 13.13.0, 14.2.0

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External links
https://downloads.asterisk.org/pub/security/AST-2016-008.html
https://downloads.asterisk.org/pub/security/AST-2016-008-13.diff
https://downloads.asterisk.org/pub/security/AST-2016-008-14.diff
https://www.securityfocus.com/bid/94792
https://www.securitytracker.com/id/1037407
https://issues.asterisk.org/jira/browse/ASTERISK-26579

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.