#VU69511 NULL pointer dereference in Certified Asterisk and Asterisk Open Source - CVE-2021-46837

Vulnerability identifier: #VU69511

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-2021-46837

CWE-ID: CWE-476

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Certified Asterisk
Server applications / Conferencing, Collaboration and VoIP solutions
Asterisk Open Source
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 a NULL pointer dereference error. A remote attacker can send an m=image line and zero port in a response to a T.38 re-invite initiated by Asterisk and perform a denial of service (DoS) attack.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Certified Asterisk: before 16.8-cert7, 16.8-cert7

Asterisk Open Source: before 17.9.3, 18.3.0, 17.9.3, 17.9.3

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External links
https://downloads.asterisk.org/pub/security/AST-2021-006.html
https://lists.debian.org/debian-lts-announce/2022/11/msg00021.html
https://www.debian.org/security/2022/dsa-5285

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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.