CVE-2020-14928

What it actually does

The vulnerability is a STARTTLS buffering flaw in evolution-data-server that causes additional data following a server "begin TLS" response to be read and processed within an established TLS context for SMTP and POP3, enabling response injection that can result in command execution or protocol manipulation.

Why it matters to the business

Organizations using affected versions face risk of email account compromise or data tampering over SMTP/POP3 connections, increasing exposure to unauthorized access; the issue has been public for years with public exploits available, though low EPSS indicates limited observed in-the-wild use so far.

How an attack unfolds

An attacker intercepts or proxies SMTP/POP3 traffic, waits for the server STARTTLS response, injects crafted data that gets buffered and later interpreted inside the TLS session, and uses the resulting command injection to issue unauthorized protocol commands or exfiltrate credentials without proper TLS protection.

How to fix it

Upgrade evolution-data-server to the fixed commit ba82be72cfd427b5d72ff21f929b3a6d8529c4df or later releases that contain the buffering fix; rebuild and redeploy any dependent applications; verify no custom builds retain the vulnerable code paths.

How to confirm the fix worked

Confirm the installed package reports a version containing commit ba82be72cfd427b5d72ff21f929b3a6d8529c4df; run regression tests exercising STARTTLS negotiation on SMTP and POP3; monitor for unexpected protocol responses during encrypted sessions.

Typical attack path

1. Position as network intermediary on SMTP or POP3 traffic path
2. Observe client connection and server STARTTLS response
3. Inject additional protocol data into the response buffer
4. Allow client to proceed into TLS session where injected data is processed
5. Execute injected commands to manipulate authentication, retrieve messages, or alter session state

How to detect it

Search mail server and client logs for unexpected protocol data immediately after STARTTLS responses; inspect network captures for injected commands inside what should be TLS-protected sessions; review process execution logs for anomalous SMTP or POP3 command sequences originating from the affected library.

• unexpected data following STARTTLS 220 response in SMTP/POP3 logs
• TLS session containing protocol commands not preceded by proper handshake completion
• evolution-data-server process handling injected responses in SMTP or POP3 flows

What your security team should do

• Prioritize patching all instances of evolution-data-server to the fixed commit within standard change windows
• Review email client configurations that rely on this library and enforce certificate pinning where possible
• Add network monitoring for anomalous SMTP/POP3 traffic patterns during TLS negotiation