Vulnerability identifier: #VU22936

Vulnerability risk: Medium

CVSSv3.1: 6.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2019-18976

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: No

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

Vendor: Digium (Linux Support Services)

Description

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

The vulnerability exists due to insufficient validation of user-supplied input in the "res_pjsip_t38.c" module. A remote attacker can cause a denial of service condition when Asterisk receives a re-invite initiating T.38 faxing and has a port of 0 and no c line in the SDP.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Asterisk Open Source: 13.0.0 - 13.29.1

Certified Asterisk: 13.21 - 13.21-cert4

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External links
http://seclists.org/fulldisclosure/2019/Nov/20
http://issues.asterisk.org/jira/browse/ASTERISK-28612

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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.