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[Critical] SSH20Cisco125 Vulnerability
Please confirm remediation by [Date].
Using ssh-mitm or a custom script, the attacker can intercept a new SSH connection, present the factored private key, and transparently proxy traffic. The admin sees a normal SSH prompt, but all commands are logged. ssh20cisco125 vulnerability
Simply patching is not enough for this vulnerability. The backdoor persists on the filesystem. You must check for indicators of compromise (IoCs).
RSA security relies on the difficulty of factoring the product of two large primes (n = p × q). With a 1024-bit modulus (128 bytes), factoring is extremely difficult for most attackers. However, 1000-bit (125 bytes) is an odd, weaker size. [Critical] SSH20Cisco125 Vulnerability
A vulnerability existed in the SSH2 (Secure Shell version 2) implementation of Cisco AireOS software, notably impacting the 2500 series controllers. An unauthenticated, remote attacker could exploit this flaw by sending a crafted SSH packet to the controller’s management interface.
From an external Linux host:
nmap --script ssh2-enum-algos -p 22 <cisco-ip>
Then use a tool like ssh-audit:
ssh-audit <cisco-ip> | grep -i "modulus"
If output shows rsa 1000 or modulus size: 125, you are vulnerable. Please confirm remediation by [Date]
Once the private key is factored, the attacker can generate valid host keys and install a persistent backdoor (e.g., a rogue admin account) without triggering alarms, because the SSH host key remains unchanged.
If you have not patched your Cisco IOS XE devices recently, you must take action immediately.
[Critical] SSH20Cisco125 Vulnerability
Please confirm remediation by [Date].
Using ssh-mitm or a custom script, the attacker can intercept a new SSH connection, present the factored private key, and transparently proxy traffic. The admin sees a normal SSH prompt, but all commands are logged.
Simply patching is not enough for this vulnerability. The backdoor persists on the filesystem. You must check for indicators of compromise (IoCs).
RSA security relies on the difficulty of factoring the product of two large primes (n = p × q). With a 1024-bit modulus (128 bytes), factoring is extremely difficult for most attackers. However, 1000-bit (125 bytes) is an odd, weaker size.
A vulnerability existed in the SSH2 (Secure Shell version 2) implementation of Cisco AireOS software, notably impacting the 2500 series controllers. An unauthenticated, remote attacker could exploit this flaw by sending a crafted SSH packet to the controller’s management interface.
From an external Linux host:
nmap --script ssh2-enum-algos -p 22 <cisco-ip>
Then use a tool like ssh-audit:
ssh-audit <cisco-ip> | grep -i "modulus"
If output shows rsa 1000 or modulus size: 125, you are vulnerable.
Once the private key is factored, the attacker can generate valid host keys and install a persistent backdoor (e.g., a rogue admin account) without triggering alarms, because the SSH host key remains unchanged.
If you have not patched your Cisco IOS XE devices recently, you must take action immediately.
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