Vulnerability identifier: #VU53315

Vulnerability risk: Medium

CVSSv3.1: 4.2 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-32919

CWE-ID: CWE-287

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Prosody
Server applications / Mail servers

Vendor: Prosody

Description

The vulnerability allows a remote attacker to bypass authentication process.

The vulnerability exists due to an error in when processing authentication requests. The undocumented dialback_without_dialback option in mod_dialback enables an experimental feature for server-to-server authentication. It does not correctly authenticate remote server certificates, allowing a remote server to impersonate another server.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Prosody: 0.11.0 - 0.11.8

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External links
http://blog.prosody.im/prosody-0.11.9-released/
http://www.openwall.com/lists/oss-security/2021/05/13/1
http://www.openwall.com/lists/oss-security/2021/05/14/2

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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.