Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
Sources: National Vulnerability Database, CISA KEV, Exploit-DB
CVE-2025-20155 Overview
CVE-2025-20155 is an arbitrary file write vulnerability in the bootstrap loading component of Cisco IOS XE Software. The flaw affects devices deployed in Software-Defined WAN (SD-WAN) mode or configured with SD-Routing. An authenticated local attacker with high privileges can modify a bootstrap file generated by Cisco Catalyst SD-WAN Manager, load it to device flash, and trigger file writes to the underlying operating system during device reload or SD-Routing configuration. The vulnerability is classified under CWE-1287: Improper Validation of Specified Type of Input.
Critical Impact
Successful exploitation allows arbitrary file writes to the underlying operating system of affected Cisco IOS XE devices, potentially enabling persistence or configuration tampering on SD-WAN and SD-Routing deployments.
Affected Products
- Cisco IOS XE Software versions 17.9.4 through 17.9.6a
- Cisco IOS XE Software versions 17.12.1 through 17.12.4b
- Cisco IOS XE Software versions 17.13.1, 17.13.1a, 17.14.1, and 17.14.1a
Discovery Timeline
- 2025-05-07 - CVE-2025-20155 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-20155
Vulnerability Analysis
The vulnerability resides in how Cisco IOS XE Software parses and loads the bootstrap configuration file during initial SD-WAN deployment or SD-Routing provisioning. The system software reads this bootstrap file without sufficient validation of its contents. An attacker who can place a crafted bootstrap file into the device flash can influence file write operations performed by the loading routine.
Exploitation requires authenticated local access with high privileges, which limits the attack to users who already hold administrative control of the device flash. However, a successful write to the underlying operating system can be used to stage persistence, overwrite configuration artifacts, or tamper with files consumed by other services on the device.
Root Cause
The root cause is insufficient input validation of the bootstrap file consumed during two specific workflows: green field SD-WAN deployment and SD-Routing configuration. The loader trusts fields in the bootstrap file that control file placement on the underlying Linux-based operating system. Because the parser does not enforce the expected input type and path constraints, attacker-controlled values flow into file write operations, producing the [CWE-1287] condition.
Attack Vector
The attack vector is local and requires authentication. An attacker modifies a bootstrap file originally generated by Cisco Catalyst SD-WAN Manager, uploads it to the device flash, and then either reloads the device in SD-WAN mode or applies an SD-Routing configuration. During the subsequent bootstrap parsing, the crafted entries cause the system to write arbitrary files to the underlying operating system. No user interaction beyond the attacker-initiated reload or configuration change is required. Refer to the Cisco Security Advisory for complete technical details.
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Stop Exploit AttemptsDetection Methods for CVE-2025-20155
Indicators of Compromise
- Unexpected or recently modified bootstrap configuration files present in device flash prior to a reload event.
- Unauthorized files appearing in operating system directories after an SD-WAN green field boot or SD-Routing configuration change.
- Device reloads or SD-Routing configuration events initiated outside of approved change windows.
Detection Strategies
- Compare bootstrap files on device flash against the authoritative versions issued by Cisco Catalyst SD-WAN Manager and alert on hash mismatches.
- Review Cisco IOS XE command history and AAA logs for copy operations writing bootstrap files to flash by non-automation accounts.
- Correlate device reload events in SD-WAN mode with preceding flash modifications to identify suspicious sequences.
Monitoring Recommendations
- Forward Cisco IOS XE syslog and AAA accounting records to a centralized SIEM for retention and correlation.
- Monitor administrative access to SD-WAN Manager and privileged shell access on IOS XE devices for anomalous sessions.
- Track file integrity on SD-WAN Manager hosts that generate bootstrap files to detect upstream tampering.
How to Mitigate CVE-2025-20155
Immediate Actions Required
- Apply the fixed Cisco IOS XE Software releases referenced in the Cisco Security Advisory cisco-sa-bootstrap-KfgxYgdh.
- Audit all accounts with privileged access to device flash and SD-WAN Manager, and revoke credentials that are no longer required.
- Validate bootstrap files loaded into flash against known-good copies before any device reload or SD-Routing configuration.
Patch Information
Cisco has published fixed software releases for CVE-2025-20155 through the vendor advisory cisco-sa-bootstrap-KfgxYgdh. Administrators should consult the advisory for the specific first-fixed release that corresponds to their deployed train (17.9, 17.12, 17.13, or 17.14) and schedule upgrades accordingly. No workarounds that fully address the vulnerability are published by the vendor.
Workarounds
- Restrict administrative access to Cisco Catalyst SD-WAN Manager and to the IOS XE device flash to a minimal, audited set of operators.
- Enforce out-of-band verification of bootstrap files before green field SD-WAN deployment or SD-Routing configuration.
- Enable AAA command accounting and file integrity monitoring to detect unauthorized bootstrap file modifications prior to a reload.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
Sources: National Vulnerability Database, CISA KEV, Exploit-DB
