CVE-2020-14929 – This CVE affects Alpine email client versions b... (How to Fix)

Q: What is the severity of CVE-2020-14929?

CVE-2020-14929 has a CVSS score of 7.5 (HIGH). This CVE affects Alpine email client versions before 2.23, where sending a /tls command during PREAUTH causes the client to silently fall back to insecure connections instead of terminating. This vulnerability allows man-in-the-middle attackers to intercept email communications when users attempt to establish secure connections.

📋 TL;DR

This CVE affects Alpine email client versions before 2.23, where sending a /tls command during PREAUTH causes the client to silently fall back to insecure connections instead of terminating. This vulnerability allows man-in-the-middle attackers to intercept email communications when users attempt to establish secure connections.

💻 Affected Systems

Products:

Alpine email client

Versions: All versions before 2.23

Operating Systems: Linux, Unix-like systems

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects connections using PREAUTH where /tls command is sent. Requires user interaction to trigger the vulnerable code path.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Attackers intercept sensitive email communications including credentials, personal data, and confidential information through man-in-the-middle attacks.

🟠

Likely Case

Email content interception in insecure network environments, potentially exposing sensitive communications.

🟢

If Mitigated

Limited impact if email servers enforce TLS-only connections or if network traffic is already encrypted at lower layers.

🌐 Internet-Facing: MEDIUM - Requires attacker to be in position to intercept network traffic between client and server.

🏢 Internal Only: LOW - Internal networks typically have better security controls and monitoring.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires man-in-the-middle position and user to send /tls command during PREAUTH. No public exploit code has been disclosed.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 2.23 and later

Vendor Advisory: http://mailman13.u.washington.edu/pipermail/alpine-info/2020-June/008989.html

Restart Required: No

Instructions:

1. Download Alpine 2.23 or later from official repository. 2. Compile and install according to distribution instructions. 3. Replace existing Alpine binary with patched version.

🔧 Temporary Workarounds

Disable PREAUTH

linux

Configure Alpine to not use PREAUTH authentication method

Edit alpine configuration to remove PREAUTH options

Force TLS connections

all

Configure email server to require TLS and reject insecure connections

🧯 If You Can't Patch

Use alternative email clients that are not vulnerable
Ensure all network traffic is encrypted using VPN or other network-level encryption

🔍 How to Verify

Check if Vulnerable:

Check Alpine version with 'alpine -version' or 'alpine -v' command

Check Version:

alpine -version

Verify Fix Applied:

Verify version is 2.23 or higher using 'alpine -version'

📡 Detection & Monitoring

Log Indicators:

Failed TLS handshakes followed by successful plaintext connections
Unusual connection patterns during PREAUTH

Network Indicators:

TLS negotiation failures followed by plaintext IMAP traffic
Unexpected protocol downgrades

SIEM Query:

Search for: (protocol:IMAP AND tls_handshake:failed) FOLLOWED BY (protocol:IMAP AND encryption:none) WITHIN 5s

📊 Metadata

CVE ID: CVE-2020-14929

CVSS v3 Score: 7.5 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Published: June 19, 2020

Last Updated: November 21, 2024

🔗 References

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