dbcve.org
Ios XrOperating system · Cisco

CVE-2023-20236

HIGH · 7.8 CVSS v3.1 Published 2023-09-13
Fix available
A fix is available. Upgrade to 7.10.1 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
A vulnerability in the iPXE boot function of Cisco IOS XR software could allow an authenticated, local attacker to install an unverified software image on an affected device. This vulnerability is due to insufficient image verification. An attacker could exploit this vulnerability by manipulating the boot parameters for image verification during the iPXE boot process on an affected device. A successful exploit could allow the attacker to boot an unverified software image on the affected device.

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

This vulnerability exists in the iPXE boot function of Cisco IOS XR software. The flaw allows an authenticated, local attacker to bypass image verification mechanisms by manipulating boot parameters during the iPXE boot process, enabling the installation and booting of unverified software images on affected devices.

MitigationApply the Cisco-provided patch or software update for CVE-2023-20236. Restrict local administrative access and monitor for unauthorized boot parameter modifications.

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:< 7.10.1

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 is running Cisco IOS XR
    Run 'show version' or 'cat /proc/version' (if accessible) to confirm the operating system is Cisco IOS XR
    Affected if The device does not run Cisco IOS XR (not affected)
  2. Check the installed IOS XR version
    Run 'show version' and locate the IOS XR software version number
    Affected if The version is lower than 7.10.1 (for example, 7.9.x, 7.8.x, or earlier)
  3. Determine if iPXE boot is configured
    Check the boot configuration with 'show boot' or examine the boot configuration file for iPXE-related boot parameters
    Affected if iPXE boot is enabled and the device runs a version < 7.10.1
  4. Inspect boot parameters for unauthorized modifications
    Review current boot parameters using 'show bootvar' or the boot configuration, looking for unexpected or modified boot entries
    Affected if Boot parameters have been altered to bypass image verification and the IOS XR version is < 7.10.1

The environment is affected if the device runs Cisco IOS XR version lower than 7.10.1 and has iPXE boot functionality enabled, allowing potential manipulation of boot parameters to bypass image verification.

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 7.10.1 or later
Fixed in 7.10.1
Interim mitigation

Apply the Cisco-provided patch or software update for CVE-2023-20236. Restrict local administrative access and monitor for unauthorized boot parameter modifications.

Recommended fix High confidence

Cisco IOS XR 7.10.1 or later

  1. Identify the current IOS XR version running on the affected device using 'show version' or 'admin show version'
  2. Download Cisco IOS XR version 7.10.1 or later from the Cisco Software Download Center (software.cisco.com) or Cisco sec.cloudapps.cisco.com
  3. Verify the software image integrity using the MD5/SHA256 checksums provided by Cisco before installation
  4. Follow the standard Cisco IOS XR upgrade procedure for your specific hardware platform: typically using 'install add' and 'install activate' commands in admin mode
  5. After installation, verify the new version is running using 'show version' and confirm the image verification is now properly enforced
  6. Save the configuration with 'commit' and 'wr mem' if required
Caveat Review Cisco IOS XR 7.10.1 release notes for any migration requirements or deprecated features specific to your hardware platform before upgrading

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
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,690
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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-2023-20236 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