CVE-2019-1859: Cisco Small Business Switches Secure Shell Certificate Authentication Bypass Vulnerability

Severity: high (CVSS 7.2 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2019-05-03 · updated 2026-06-17
Weakness: CWE-285

Description

A vulnerability in the Secure Shell (SSH) authentication process of Cisco Small Business Switches software could allow an attacker to bypass client-side certificate authentication and revert to password authentication. The vulnerability exists because OpenSSH mishandles the authentication process. An attacker could exploit this vulnerability by attempting to connect to the device via SSH. A successful exploit could allow the attacker to access the configuration as an administrative user if the default credentials are not changed. There are no workarounds available; however, if client-side certificate authentication is enabled, disable it and use strong password authentication. Client-side certificate authentication is disabled by default.

Affected products

Cisco Sf200-24 Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf200-24Fp Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf200-24P Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf200-48 Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf200-48P Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf250-24 Firmware: before 2.5.0.78 — fixed in 2.5.0.78
Cisco Sf250-24P Firmware: before 2.5.0.78 — fixed in 2.5.0.78
Cisco Sf250-48 Firmware: before 2.5.0.78 — fixed in 2.5.0.78
Cisco Sf250-48Hp Firmware: before 2.5.0.78 — fixed in 2.5.0.78
Cisco Sf300-08 Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf300-24 Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf300-24Mp Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf300-24P Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf300-24Pp Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf300-48 Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf300-48P Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf300-48Pp Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf302-08 Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf302-08Mp Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf302-08Mpp Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf302-08P Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf302-08Pp Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf350-48 Firmware: before 2.5.0.78 — fixed in 2.5.0.78
Cisco Sf350-48Mp Firmware: before 2.5.0.78 — fixed in 2.5.0.78
Cisco Sf350-48P Firmware: before 2.5.0.78 — fixed in 2.5.0.78
Cisco Sf500-24 Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf500-24P Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf500-48 Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf500-48P Firmware: before 1.4.10.6 — fixed in 1.4.10.6
Cisco Sf550X-24 Firmware: before 2.5.0.78 — fixed in 2.5.0.78

How to fix

Upgrade to a fixed version: Cisco Sf200-24 Firmware 1.4.10.6; Cisco Sf200-24Fp Firmware 1.4.10.6; Cisco Sf200-24P Firmware 1.4.10.6; Cisco Sf200-48 Firmware 1.4.10.6; Cisco Sf200-48P Firmware 1.4.10.6; Cisco Sf250-24 Firmware 2.5.0.78; Cisco Sf250-24P Firmware 2.5.0.78; Cisco Sf250-48 Firmware 2.5.0.78; Cisco Sf250-48Hp Firmware 2.5.0.78; Cisco Sf300-08 Firmware 1.4.10.6; Cisco Sf300-24 Firmware 1.4.10.6; Cisco Sf300-24Mp Firmware 1.4.10.6. Check the vendor advisory for mitigations.

References

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