CVE-2024-20439
Cisco Smart Licensing Utility Static Credential Vulnerability
Description
CVE-2024-20439 is a critical static credential vulnerability in Cisco Smart Licensing Utility (CSLU) that allows an unauthenticated remote attacker to gain administrative access to the application. The vulnerability exists because CSLU contains an undocumented static user credential for an administrative account, enabling any attacker who discovers this credential to log in with full administrative privileges over the CSLU API. With a CVSS v3.1 score of 9.8 and an EPSS score of 85.8% at the 99th percentile, CVE-2024-20439 was added to CISA's Known Exploited Vulnerabilities catalog with a remediation deadline of April 21, 2025, underscoring the critical nature of hardcoded credentials in network management software.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| cisco | smart license utility | >= 2.0.0, < 2.3.0 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
Weakness Type
CWE-912: Hidden Functionality
CVE-2024-20439 involves hidden functionality in the form of an undocumented static administrative account embedded within the Cisco Smart Licensing Utility. This hidden account is not documented in the product's user guide and exists as a backdoor that provides full administrative access to the CSLU API.
Learn more: CWE-912 — Hidden Functionality
CWE-798: Use of Hard-coded Credentials
The vulnerability is also classified under CWE-798 because the static credential is hardcoded into the application, meaning every installation of the affected CSLU versions shares the same administrative password. Once this credential is discovered or leaked, all unpatched instances become immediately exploitable.
Learn more: CWE-798 — Use of Hard-coded Credentials
Impact Analysis
CVE-2024-20439 has the maximum practical CVSS v3.1 score of 9.8 (Critical), reflecting the ease of exploitation and the severity of its impact. The vulnerability is network-accessible (AV:N) with low complexity (AC:L), requires no privileges (PR:N) or user interaction (UI:N). Confidentiality, integrity, and availability are all rated High because administrative access to CSLU grants full control over the licensing management API, including the ability to view and modify license configurations, access connected Cisco device information, potentially pivot to managed network devices, and disrupt licensing operations that could impact production network equipment. The EPSS score of 85.8% at the 99th percentile places this vulnerability among the most exploited, reflecting both the simplicity of exploitation (using known static credentials) and the high value of the target (enterprise network management infrastructure).
Exploit Maturity
CVE-2024-20439 demonstrates very high exploit maturity given that the static credentials have been identified and are being actively used in attacks. CISA has added it to the Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. The EPSS score of 85.8% at the 99th percentile indicates very high likelihood of exploitation. The Cisco security advisory provides details about the affected versions. Exploitation requires no specialized tools or techniques — once the static credential is known, attackers simply authenticate using standard HTTP requests to the CSLU API. The credential has been shared in security research communities, making exploitation accessible to virtually any threat actor.
Remediation
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Upgrade Cisco Smart Licensing Utility to version 2.3.0 or later immediately. This version removes the hardcoded static credential. Download the update from Cisco's security advisory page.
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Restrict network access to the CSLU interface to trusted management networks only. CSLU should never be exposed to the internet or to untrusted network segments. Implement firewall rules to allow access only from authorized management workstations and IP ranges.
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Audit CSLU access logs for unauthorized authentication events. Review logs for logins using the static administrative credential, unexpected API calls, license configuration changes, or access from unfamiliar IP addresses. Any unauthorized access should trigger an immediate incident response investigation.
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Assess the blast radius of any confirmed compromise. If the CSLU instance was accessed by an unauthorized party, review all Cisco devices and licenses managed through the compromised instance. Check for configuration changes on managed devices and rotate any credentials that may have been exposed through the CSLU management interface.
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Implement network segmentation to isolate network management infrastructure including CSLU from general network traffic. Deploy monitoring to detect lateral movement from compromised management systems to production network devices.
Technical Details
CVE-2024-20439 is a hardcoded credential vulnerability in Cisco Smart Licensing Utility (CSLU) versions 2.0.0 through 2.2.x. The CVSS v3.1 vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H confirms this is a trivially exploitable network-accessible vulnerability with maximum impact. The vulnerability exists because the CSLU application binary contains a static username and password pair for an administrative account that is not documented in the product documentation or configuration guides. This credential is compiled into the application and is identical across all installations of the affected versions. When the CSLU service is running and accessible over the network, an attacker can authenticate to the API using these static credentials, gaining full administrative privileges. The administrative API provides capabilities including license management, device registration queries, and configuration access. The static nature of the credential means that no brute-force attack is required — the attacker simply uses the known username and password to authenticate. Cisco addressed the vulnerability in version 2.3.0 by removing the hardcoded credential and implementing proper authentication mechanisms.
Frequently Asked Questions
Is CVE-2024-20439 being actively exploited?
Yes. CISA has confirmed active exploitation by adding CVE-2024-20439 to the Known Exploited Vulnerabilities catalog. The EPSS score of 85.8% at the 99th percentile places it among the most exploited vulnerabilities, reflecting the trivial nature of exploiting hardcoded credentials.
What products are affected by CVE-2024-20439?
Cisco Smart Licensing Utility versions 2.0.0 through 2.2.x are affected. Version 2.3.0 and later have removed the hardcoded credential and are not vulnerable.
How do I fix CVE-2024-20439?
Upgrade to Cisco Smart Licensing Utility version 2.3.0 or later. There is no workaround — the hardcoded credential cannot be changed or disabled in affected versions. Restricting network access to CSLU is recommended as a compensating control until patching is complete.
How severe is CVE-2024-20439?
CVE-2024-20439 is rated Critical with a CVSS score of 9.8. The use of hardcoded credentials means exploitation is trivial — any attacker who knows the credential gains full administrative access. Its EPSS score of 85.8% confirms it is among the most actively exploited vulnerabilities.
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