CVE intelligence and bounded remediation

CVE-2019-1842 — Cisco Ios Xr Firmware security vulnerability

Medium CVSS 5.5

A vulnerability in the Secure Shell (SSH) authentication function of Cisco IOS XR Software could allow an authenticated, remote attacker to successfully log in to an affected device using two distinct usernames. The vulnerability is due to a logic error that may occur when certain sequences of actions are processed during an SSH login event on the affected device. An attacker could exploit this vulnerability by initiating an SSH session to the device with a specific sequence that presents the two usernames. A successful exploit could result in logging data misrepresentation, user enumeration, or, in certain circumstances, a command authorization bypass. See the Details section for more information.

Severity
Medium
CVSS
5.5 (2.0)
Published
2019-06-05
CISA KEV
Not currently listed
Ecosystem
operating-system
Weaknesses
CWE-285, CWE-287

Affected products

  • cisco / ios_xr_firmware / 6.1.2.tools
  • cisco / ios_xr_firmware / 6.1.3.tools
  • cisco / ios_xr_firmware / 6.2.3.tools
  • cisco / ios_xr_firmware / 6.4.2.tools

Matched remediation archetype

Authentication bypass and missing authentication

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Check exposure

  • Map every affected endpoint and protocol path, including alternate ports, legacy routes, recovery flows, service accounts, and machine-to-machine access.
  • Confirm which deployments enable the affected authentication mode and whether the interface is reachable from untrusted networks.
  • Review session, token, credential, and proxy trust configuration without attempting account takeover.

Remediate safely

  • Apply the supported fix and centralize fail-closed authentication before protected request handling.
  • Remove default or embedded credentials, rotate affected secrets and sessions, and bind authentication decisions to the intended audience and channel.
  • Add negative tests for alternate routes, malformed or absent credentials, recovery flows, and proxy-derived identity.

Authoritative sources

Complete CVE record and remediation plan

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