Ios Xr FirmwareOperating system · Cisco
CVE-2019-1842
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA logic error in Cisco IOS XR Software's SSH authentication allows an authenticated attacker to log in using two distinct usernames simultaneously. This occurs due to improper handling of sequences during SSH login events and can lead to data misrepresentation, user enumeration, or command authorization bypass.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Ios Xr FirmwareOperating system
= 6.1.2.tools= 6.1.3.tools= 6.2.3.tools= 6.4.2.toolsCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify the Cisco IOS XR firmware versionUse the 'show version' command on the IOS XR device or check the device management interface for the installed firmware versionAffected if The installed version matches 6.1.2.tools, 6.1.3.tools, 6.2.3.tools, or 6.4.2.tools
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Verify SSH service is enabledUse the 'show ssh' command or check the device configuration for 'ssh server' settingsAffected if SSH server is enabled and configured on the device
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Review SSH authentication configurationUse 'show running-config | include ssh' to examine SSH server settings and authentication methods configuredAffected if SSH authentication is configured with any method that permits interactive login
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Check for concurrent session anomaliesMonitor active SSH sessions using 'show ssh session' or review authentication logs for multiple usernames appearing in quick successionAffected if Multiple SSH sessions with different usernames from the same source IP or authentication sequence anomalies are observed
A user is affected if the device runs Cisco IOS XR firmware version 6.1.2.tools, 6.1.3.tools, 6.2.3.tools, or 6.4.2.tools with SSH server enabled and accessible.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataApply the Cisco IOS XR software update addressing CVE-2019-1842. If no patch is available, restrict SSH access to trusted networks and monitor authentication logs for anomalies.
Fix this in Ios Xr Firmware
Scoped from the published advisory
- Consultation4.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-1842 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2019-1842 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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