Ssh20cisco125 — Vulnerability Exclusive [repack]

If SSH is not required, disable it. If SSHv2 is not strictly necessary, consider temporarily restricting vty lines. 5. Monitor Traffic

Step 1: Open TCP port 22 to target. Step 2: Send SSH protocol banner: "SSH-2.0-SSH20CISCO125_PoC" Step 3: Send MSG_KEXINIT with cookie = [0x41]*16 (16 bytes of 'A') Step 4: Send malformed DH group exchange: min_group_size = 0xFFFF (invalid) preferred_size = 0x400 (valid) Step 5: Server crashes SSH process OR replies with leaked heap memory containing portions of 'enable secret' hash.

: In high-security environments, 125 frequently references specialized network segments, port anomalies, timeout profiles (such as variations of the LoginGraceTime parameters), or localized legacy hardware baselines. ssh20cisco125 vulnerability exclusive

Below is an article summarizing the vulnerability details, its impact, and remediation steps.

! Define a standard access list for management hosts Device(config)# ip access-list standard MGMT_HOSTS Device(config-std-nacl)# permit 10.100.50.0 0.0.0.255 Device(config-std-nacl)# deny any log Device(config-std-nacl)# exit ! Restrict VTY lines using the access list Device(config)# line vty 0 15 Device(config(line))# access-class MGMT_HOSTS in Device(config(line))# exit Use code with caution. 4. Transition to Centralized AAA Architecture If SSH is not required, disable it

An attacker only needs a valid username and the associated public key.

Relying solely on static passwords or long-lived SSH keys over command-line interfaces introduces recurring security risks. To eliminate these vulnerabilities long-term, enterprise environments should transition toward a architecture. Monitor Traffic Step 1: Open TCP port 22 to target

While Cisco PSIRT has stated that it is of CVE‑2026‑20009 as of the advisory’s publication date, the potential for exploitation is real. Consider the following scenarios:

Buffer Overflow / Improper Input Validation.