dbcve.org
Ios XrOperating system · Cisco

CVE-2021-1440

MEDIUM · 6.8 CVSS v3.1 Published 2024-11-18
Fix available
A fix is available. Upgrade to 7.3.1 or later.
See remediation →
77/100
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 implementation of the Resource Public Key Infrastructure (RPKI) feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause the Border Gateway Protocol (BGP) process to crash, resulting in a denial of service (DoS) condition. This vulnerability is due to the incorrect handling of a specific RPKI to Router (RTR) Protocol packet header. An attacker could exploit this vulnerability by compromising the RPKI validator server and sending a specifically crafted RTR packet to an affected device. Alternatively, the attacker could use man-in-the-middle techniques to impersonate the RPKI validator server and send a specifically crafted RTR response packet over the established RTR TCP connection to the affected device. A successful exploit could allow the attacker to cause a DoS condition because the BGP process could constantly restart and BGP routing could become unstable.Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.This advisory is part of the September 2021 release of the Cisco IOS XR Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see .

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

A vulnerability in Cisco IOS XR Software's RPKI feature allows an unauthenticated remote attacker to cause BGP process crashes via specially crafted RTR (RPKI to Router) Protocol packets. The attacker can either compromise the RPKI validator server or use man-in-the-middle techniques to send malformed RTR packets over the TCP connection, causing constant BGP process restarts and routing instability.

MitigationApply the Cisco IOS XR Software update that addresses this vulnerability. No workarounds are available. If immediate patching is not possible, consider network segmentation to limit exposure of the RPKI validator connection.

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:>= 4.3.0, < 7.3.1

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
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/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. Confirm Cisco IOS XR is running
    Run 'show version' or 'uname -a' to identify the operating system. Look for 'IOS XR' in the output.
    Affected if The device is not running Cisco IOS XR software
  2. Check the IOS XR version
    Run 'show version' and locate the software version number (e.g., 5.3.2, 7.0.1). Compare against the affected range: >= 4.3.0 and < 7.3.1.
    Affected if The installed version falls within >= 4.3.0 and < 7.3.1
  3. Verify if RPKI feature is enabled
    Run 'show rpki summary' or 'show rpki configuration' in EXEC mode. If the command is unrecognized or returns no data, RPKI is likely not enabled.
    Affected if RPKI feature is enabled and configured on the device
  4. Check for RTR (RPKI-to-Router) protocol configuration
    Run 'show running-config | include rtr' or 'show rpki connections' to see if an RTR session to an RPKI validator is configured.
    Affected if An active RTR connection to an external RPKI validator server exists

A device is affected if it runs Cisco IOS XR version 4.3.0 through 7.3.0 with the RPKI feature enabled and an RTR session configured to an RPKI validator server.

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 7.3.1 or later
Fixed in 7.3.1
Interim mitigation

Apply the Cisco IOS XR Software update that addresses this vulnerability. No workarounds are available. If immediate patching is not possible, consider network segmentation to limit exposure of the RPKI validator connection.

Recommended fix High confidence

Cisco IOS XR 7.3.1 or later (September 2021 Security Advisory release)

  1. Verify current IOS XR version with 'show version' command
  2. Download Cisco IOS XR software version 7.3.1 or later from Cisco.com (requires valid service contract)
  3. Back up current configuration using 'admin commit backup' or 'copy running-config bootflash:'
  4. Transfer the new software image to the device's bootflash or network storage
  5. Verify image integrity using 'verify /md5' or 'verify sha256' commands
  6. Schedule maintenance window as BGP will be impacted during upgrade
  7. Install the new software package using 'install add file <image> activate commit' command
  8. Verify the installation completed successfully with 'show install active'
Caveat Standard IOS XR upgrade may cause brief BGP peering disruption; verify hardware compatibility and review release notes for any migration considerations

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

Fix this in Ios Xr Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-1440 — 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-2021-1440 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