Table of Contents
- Are Your Servers at Risk? Critical OpenSSH Vulnerabilities Explained
- What Is OpenSSH?
- Vulnerability #1: CVE-2024-12797 (OpenSSL Issue)
- Vulnerabilities #2 & #3: CVE-2025-26465 and CVE-2025-26466 (OpenSSH Issues)
- CVE-2025-26465: Man-in-the-Middle Attack
- CVE-2025-26466: Denial-of-Service Attack
- How to Fix These Issues
- Step 1: Update Your Software
- Step 2: Harden Your Server Settings
Are Your Servers at Risk? Critical OpenSSH Vulnerabilities Explained
Hackers love finding cracks in software, and OpenSSH just gave them a few. Security researchers discovered three vulnerabilities that could let attackers mess with your systems. If you use OpenSSH or OpenSSL, you need to act fast. Let’s break it down.
What Is OpenSSH?
Think of OpenSSH as the bodyguard for your data. It allows secure communication over sketchy networks. Instead of sending sensitive info in plain text (like shouting secrets in a crowded room), it encrypts everything, keeping it private. It’s popular on Linux, macOS, and other operating systems for remote logins, file transfers, and tunneling.
Vulnerability #1: CVE-2024-12797 (OpenSSL Issue)
This one’s tricky. It affects OpenSSL versions 3.2, 3.3, and 3.4 when using something called Raw Public Keys (RPKs). Here’s what happens:
The Problem: When a server isn’t authenticated properly, the connection handshake doesn’t fail like it should. This opens the door to man-in-the-middle attacks where hackers can intercept your data.
Who’s Safe? If you’re using OpenSSL 3.1 or older versions (like 1.1.1), you’re fine.
What to Do: Update to the latest versions:
- OpenSSL 3.4 > Upgrade to 3.4.1
- OpenSSL 3.3 > Upgrade to 3.3.2
- OpenSSL 3.2 > Upgrade to 3.2.4
Vulnerabilities #2 & #3: CVE-2025-26465 and CVE-2025-26466 (OpenSSH Issues)
CVE-2025-26465: Man-in-the-Middle Attack
What Happens: If the VerifyHostKeyDNS option is enabled in your OpenSSH client, attackers can intercept your connection without much effort—even if you didn’t configure DNS records for SSH keys!
Good News: This option is off by default unless you’re using FreeBSD (it was enabled there until March 2023).
CVE-2025-26466: Denial-of-Service Attack
What Happens: Hackers can overload the server or client before authentication even starts, draining memory and CPU resources like a leaky faucet wasting water.
Who’s Affected: All OpenSSH versions from 6.8p1 to 9.9p1 are at risk for this attack.
How to Fix These Issues
Step 1: Update Your Software
For OpenSSL: Use versions 3.4.1, 3.3.2, or 3.2.4 depending on what you’re running.
For OpenSSH: Upgrade to version 9.9p2 immediately.
Step 2: Harden Your Server Settings
Use options like LoginGraceTime, MaxStartups, and PerSourcePenalties to limit abuse.
Over 71 million OpenSSH services are out there, making them juicy targets for hackers if left unpatched. These vulnerabilities aren’t just technical hiccups—they’re open doors for attacks that could cost time, money, and trust.
Don’t wait until it’s too late—patch your systems now! Staying updated is like locking your doors at night; it’s basic but essential for security.