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Ios XeOperating system · Cisco

CVE-2025-20155

MEDIUM · 6.0 CVSS v3.1 Published 2025-05-07
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
Remediation priority · Elevated
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 bootstrap loading of Cisco IOS XE Software could allow an authenticated, local attacker to write arbitrary files to an affected system. This vulnerability is due to insufficient input validation of the bootstrap file that is read by the system software when a device is first deployed in SD-WAN mode or when an administrator configures SD-Routing on the device. An attacker could exploit this vulnerability by modifying a bootstrap file generated by Cisco Catalyst SD-WAN Manager, loading it into the device flash, and then either reloading the device in a green field deployment in SD-WAN mode or configuring the device with SD-Routing. A successful exploit could allow the attacker to perform arbitrary file writes to the underlying operating system.

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

This vulnerability exists in the bootstrap loading mechanism of Cisco IOS XE Software. When a device is deployed in SD-WAN mode (green field) or configured with SD-Routing, it reads a bootstrap file generated by Cisco Catalyst SD-WAN Manager from device flash. Due to insufficient input validation of this bootstrap file, an authenticated local attacker who can modify the bootstrap file can achieve arbitrary file writes to the underlying operating system.

MitigationRestrict physical and administrative access to devices to prevent unauthorized modification of bootstrap files. Validate bootstrap file integrity through Cisco-provided mechanisms before loading. Monitor for unauthorized changes to flash storage. Apply Cisco IOS XE patches when released.

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 XeOperating system
Affected:= 17.9.4= 17.9.4a= 17.9.5= 17.9.5a= 17.9.5b= 17.9.5e= 17.9.5f= 17.9.6= 17.9.6a= 17.11.99sw= 17.12.1= 17.12.1a

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

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/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 installed IOS XE version
    Execute 'show version' on the device CLI and locate the IOS XE release string (for example, 17.9.5 or 17.12.1)
    Affected if The version matches any of these: 17.9.4, 17.9.4a, 17.9.5, 17.9.5a, 17.9.5b, 17.9.5e, 17.9.5f, 17.9.6, 17.9.6a, 17.11.99sw, 17.12.1, or 17.12.1a
  2. Determine if device is in SD-WAN mode
    Run 'show sdwan version' or check the boot variable with 'show boot' to see if the device was deployed via SD-WAN zero-touch provisioning (green field)
    Affected if The device shows as SD-WAN enabled or was deployed in SD-WAN mode
  3. Check for SD-Routing configuration
    Run 'show running-config | include sd-routing' or look for SD-Routing related configuration in the device config
    Affected if SD-Routing feature is configured on the device
  4. Locate bootstrap files on flash storage
    Execute 'dir flash:' or 'show flash:' to list files on the device flash. Look for files with bootstrap-related naming such as .bootstrap extensions or sdwan_bootstrap files
    Affected if Bootstrap files generated by Cisco Catalyst SD-WAN Manager exist on the device flash

A device is affected if it runs any of the listed IOS XE versions AND is deployed in SD-WAN mode (green field) or has SD-Routing configured, with a bootstrap file present on flash that could be modified by an authenticated local attacker.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Restrict physical and administrative access to devices to prevent unauthorized modification of bootstrap files. Validate bootstrap file integrity through Cisco-provided mechanisms before loading. Monitor for unauthorized changes to flash storage. Apply Cisco IOS XE patches when released.

Recommended fix Moderate confidence

IOS XE 17.9.6 or later (17.9.x train)

  1. 1. Verify current IOS XE version by running 'show version' on the device
  2. 2. Confirm the device is running one of the affected versions: 17.9.4, 17.9.4a, 17.9.5, or 17.9.5a
  3. 3. Download the fixed IOS XE release (17.9.6 or later) from Cisco Software Central (software.cisco.com)
  4. 4. Back up the current device configuration using 'copy running-config tftp:' or 'write memory'
  5. 5. If using SD-WAN, also back up the bootstrap configuration files from flash
  6. 6. Upgrade the IOS XE software image using 'software install file <image> new' command
  7. 7. After upgrade, verify the new version is running with 'show version'
  8. 8. Reload the device if required by the upgrade process
Caveat Review Cisco IOS XE 17.9.6 release notes for any configuration changes, especially related to SD-WAN/SD-Routing functionality; some SD-WAN templates may require re-provisioning after upgrade

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

Fix this in Ios Xe Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
30.0 hours of engineering $5,280
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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-2025-20155 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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