dbcve.org
Ios XrOperating system · Cisco

CVE-2021-34728

HIGH · 7.8 CVSS v3.1 Published 2021-09-09
Fix available
A fix is available. Upgrade to 7.3.2 / 7.4.1 or later.
See remediation →
80/100
Remediation priority · High
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
Multiple vulnerabilities in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker with a low-privileged account to elevate privileges on an affected device. For more information about these vulnerabilities, see the Details section of this advisory.

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 · moderate confidence

Multiple vulnerabilities in the Cisco IOS XR Software CLI allow an authenticated local attacker with low-privileged account access to elevate privileges to higher permission levels. The vulnerabilities stem from insufficient validation of CLI command inputs, enabling privilege escalation. Successful exploitation grants the attacker root or administrative-level access on affected Cisco IOS XR devices.

MitigationApply Cisco IOS XR software updates or patches as released. If patches are unavailable, restrict local CLI access to trusted only and monitor for unauthorized privilege escalation attempts.

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:< 7.3.2>= 7.4.0, < 7.4.1

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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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 the device OS and version
    Execute 'show version' on the Cisco device CLI and locate the IOS XR version number in the output
    Affected if The displayed IOS XR version falls within < 7.3.2 or >= 7.4.0 but < 7.4.1
  2. Verify local CLI authentication is enabled
    Check the configuration with 'show running-config | include aaa' and look for authentication settings for line con0 or tty lines
    Affected if Local authentication is configured for console or tty lines, allowing low-privileged user logins
  3. Confirm presence of low-privileged accounts
    Execute 'show users all' to list all configured users and their privilege levels
    Affected if There exist user accounts with privilege level below 15 (non-root/administrator) who can access the CLI
  4. Check current user privilege context
    Execute 'show privilege' to display the current session privilege level
    Affected if The current logged-in user has privilege level less than 15 (non-administrative)

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.

dbcve · scoped
Upgrade available Upgrade to 7.3.2 / 7.4.1 or later
Fixed in 7.3.27.4.1
Interim mitigation

Apply Cisco IOS XR software updates or patches as released. If patches are unavailable, restrict local CLI access to trusted only and monitor for unauthorized privilege escalation attempts.

Recommended fix High confidence

Upgrade to IOS XR 7.3.2 or later in the 7.3.x train, or 7.4.1 or later in the 7.4.x train

  1. Identify current IOS XR version using 'show version' command
  2. Determine appropriate upgrade path based on current version (7.3.x line or 7.4.x line)
  3. Access Cisco.com software downloads to obtain the fixed release (requires valid Cisco service contract)
  4. Review Cisco IOS XR upgrade documentation and release notes for the target version
  5. Schedule a maintenance window considering device reboot time
  6. Backup current device configuration to a secure location
  7. Transfer the fixed software image to the device using TFTP, FTP, or SCP
  8. Execute upgrade procedure using 'install' commands per Cisco IOS XR upgrade guide
Caveat Review release notes for potential compatibility issues, as major version upgrades may require additional migration steps and could affect feature compatibility

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Ios Xr Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-34728 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2021-34728 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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