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Ios XrOperating system · Cisco

CVE-2019-1681

HIGH · 7.5 CVSS v3.1 Published 2019-02-21
Fix available
A fix is available. Upgrade to 6.5.2 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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 · unedited
A vulnerability in the TFTP service of Cisco Network Convergence System 1000 Series software could allow an unauthenticated, remote attacker to retrieve arbitrary files from the targeted device, possibly resulting in information disclosure. The vulnerability is due to improper validation of user-supplied input within TFTP requests processed by the affected software. An attacker could exploit this vulnerability by using directory traversal techniques in malicious requests sent to the TFTP service on a targeted device. An exploit could allow the attacker to retrieve arbitrary files from the targeted device, resulting in the disclosure of sensitive information. This vulnerability affects Cisco IOS XR Software releases prior to Release 6.5.2 for Cisco Network Convergence System 1000 Series devices when the TFTP service is enabled.

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 confidence

Directory traversal vulnerability in Cisco NCS 1000 Series TFTP service allows unauthenticated remote attackers to escape the TFTP root directory and read arbitrary files from the device filesystem by using '..' sequences in TFTP request filenames. The TFTP server fails to properly validate/sanitize the filename parameter.

MitigationDisable the TFTP service if not required, or upgrade to Cisco IOS XR Software Release 6.5.2 or later. Apply network access controls to limit TFTP service exposure to trusted sources.

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 XrOperating system
Affected:< 6.5.2

CVSS 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
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify device model and IOS XR version
    Run 'show version' or 'show hardware' to determine if the device is Cisco NCS 1000 Series or Cisco IOS XR, and note the software version number.
    Affected if The device is Cisco NCS 1000 Series or Cisco IOS XR running a version earlier than 6.5.2.
  2. Verify TFTP service is enabled
    Run 'show tftp server' or check the configuration with 'show running-config | include tftp' to see if the TFTP service is configured and active.
    Affected if TFTP service is enabled and running on the device.
  3. Confirm TFTP server configuration
    Run 'show tftp server configuration' or 'show tftp vrfs' to examine the TFTP server settings, including the root directory and access controls.
    Affected if TFTP server is configured without proper path validation or with permissive access settings.
  4. Check TFTP port accessibility
    Verify if UDP port 69 (TFTP) is open and listening externally using 'show tcp brief all' or by scanning the device from an external interface.
    Affected if TFTP port 69 is accessible from untrusted or external networks.

The device is affected if it is a Cisco NCS 1000 Series or Cisco IOS XR device running version earlier than 6.5.2 with TFTP service enabled and accessible.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Upgrade available Upgrade to 6.5.2 or later
Fixed in 6.5.2
Interim mitigation

Disable the TFTP service if not required, or upgrade to Cisco IOS XR Software Release 6.5.2 or later. Apply network access controls to limit TFTP service exposure to trusted sources.

Fix this in Ios Xr Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2019-1681 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data