An issue was discovered in Prosody before 0.11.9. 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 (when this option is enabled).

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-32919
• https://blog.prosody.im/prosody-0.11.9-released/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/6MFFBZWXKPZEVZNQSVJNCUE7WRF3T7DG/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GUN63AHEWB2WRROJHU3BVJRWLONCT2B7/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LWJ2DG2DFJOEFEWOUN26IMYYWGSA2ZEE/
• https://security.gentoo.org/glsa/202105-15
• https://www.debian.org/security/2021/dsa-4916
• http://www.openwall.com/lists/oss-security/2021/05/13/1
• http://www.openwall.com/lists/oss-security/2021/05/14/2