CVE-2025-20317: Cisco IMC vKVM XSS Vulnerability

CVE-2025-20317 Overview

A vulnerability in the Virtual Keyboard Video Monitor (vKVM) connection handling of Cisco Integrated Management Controller (IMC) could allow an unauthenticated, remote attacker to redirect a user to a malicious website. This vulnerability is due to insufficient verification of vKVM endpoints, which can be exploited by persuading a user to click a crafted link. A successful exploit could allow the attacker to redirect a user to a malicious webpage and potentially capture user credentials.

Critical Impact

Unauthenticated attackers can redirect users to malicious websites via crafted links, potentially leading to credential theft and further compromise of enterprise infrastructure management systems.

Affected Products

• Cisco Integrated Management Controller (IMC)
• Cisco UCS Manager (includes affected vKVM client)
• Systems utilizing Cisco vKVM for remote management

Discovery Timeline

• 2025-08-27 - CVE-2025-20317 published to NVD
• 2025-08-29 - Last updated in NVD database

Technical Details for CVE-2025-20317

Vulnerability Analysis

This vulnerability is classified as CWE-601 (URL Redirection to Untrusted Site, also known as Open Redirect). The flaw resides in the vKVM connection handling mechanism within Cisco Integrated Management Controller, which fails to properly validate endpoint destinations before redirecting users.

Open redirect vulnerabilities occur when an application accepts user-controlled input that specifies a link to an external site and uses that link in a redirect. By leveraging this flaw, attackers can craft URLs that appear legitimate (originating from trusted Cisco IMC infrastructure) but ultimately redirect victims to attacker-controlled domains.

The network-based attack vector requires user interaction, specifically persuading an administrator or user to click a malicious link. Once clicked, the victim is seamlessly redirected to an attacker-controlled site designed to harvest credentials or deliver malware, while believing they are still interacting with legitimate Cisco infrastructure.

Root Cause

The root cause is insufficient verification of vKVM endpoints within the Cisco IMC connection handling logic. The application fails to properly validate or sanitize URL parameters used in redirect operations, allowing attackers to specify arbitrary external destinations. This lack of endpoint verification enables attackers to abuse the trust users place in Cisco IMC URLs to redirect them to malicious sites.

Attack Vector

The attack is network-based and requires user interaction. An attacker would craft a malicious URL containing the legitimate Cisco IMC hostname with manipulated redirect parameters pointing to an attacker-controlled domain. The attacker then delivers this link to potential victims through phishing emails, malicious websites, or other social engineering techniques.

When a user clicks the crafted link expecting to access their legitimate vKVM console, the vulnerable IMC application processes the malicious redirect parameter and sends the user to the attacker's website. The attacker's site can then present a convincing login page to harvest credentials, or serve malicious payloads. This technique is particularly effective as the initial URL appears to originate from trusted internal infrastructure.

Detection Methods for CVE-2025-20317

Indicators of Compromise

• Unusual redirect patterns in Cisco IMC/vKVM access logs showing external destination URLs
• User reports of being redirected to unexpected websites when accessing vKVM consoles
• Phishing emails containing links to your organization's Cisco IMC endpoints with suspicious URL parameters
• Authentication attempts from unexpected IP addresses following vKVM redirect activity

Detection Strategies

• Monitor and analyze HTTP request logs from Cisco IMC for redirect requests containing external or suspicious destination URLs
• Implement web proxy or firewall rules to alert on redirects from IMC infrastructure to non-whitelisted domains
• Deploy email security solutions to detect and block phishing attempts containing crafted IMC/vKVM URLs
• Review browser history and network traffic logs for patterns indicating redirect abuse

Monitoring Recommendations

• Enable verbose logging on Cisco IMC systems and forward logs to a centralized SIEM for analysis
• Establish baseline patterns of normal vKVM access and alert on deviations, particularly redirect activity
• Monitor for new phishing campaigns targeting your organization that reference Cisco IMC or vKVM infrastructure
• Implement real-time alerting for authentication failures following suspicious redirect activity

How to Mitigate CVE-2025-20317

Immediate Actions Required

• Review the Cisco Security Advisory for specific patch availability and remediation guidance
• Educate administrators and users about the risks of clicking links in emails or messages claiming to provide vKVM access
• Implement URL filtering and web proxy policies to block redirects from IMC infrastructure to untrusted external domains
• Consider restricting access to Cisco IMC interfaces to trusted networks and IP ranges only

Patch Information

Cisco has released information regarding this vulnerability in their security advisory. Administrators should consult the Cisco Security Advisory for specific software versions affected and available patches. Apply the vendor-recommended software updates as soon as possible to remediate this vulnerability.

Workarounds

• Restrict network access to Cisco IMC management interfaces using firewall rules or ACLs to limit exposure
• Train users to access vKVM consoles by typing the URL directly or using bookmarks rather than clicking links from emails or external sources
• Implement multi-factor authentication for IMC access to reduce the impact of potential credential theft
• Deploy browser extensions or security solutions that warn users about redirects to unfamiliar domains

# Example: Restrict IMC access to management network only (firewall rule concept)
# Adjust for your specific firewall platform and network configuration
# Limit access to Cisco IMC interface to trusted management subnet
iptables -A INPUT -p tcp --dport 443 -s 10.0.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP