CVE-2018-0155
Cisco Catalyst Bidirectional Forwarding Detection Denial-of-Service Vulnerability
Description
CVE-2018-0155 is a denial-of-service vulnerability in Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches. A vulnerability in the Bidirectional Forwarding Detection (BFD) offload implementation of Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches could allow an unauthenticated, remote attacker to cause a crash of the iosd process, causing a denial-of-service (DoS) condition. Successful exploitation could result in denial of service through system crashes on affected devices. CISA has added CVE-2018-0155 to the Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. The EPSS score of 11.22% (93.4rd percentile) indicates a high likelihood of exploitation activity.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| cisco | ios | 3.6\(2\)e |
| cisco | ios xe | 3.6\(2\)e |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
References
- http://www.securityfocus.com/bid/103565(Third Party Advisory, VDB Entry)
- http://www.securitytracker.com/id/1040587(Third Party Advisory, VDB Entry)
- https://ics-cert.us-cert.gov/advisories/ICSA-18-107-05(Third Party Advisory, US Government Resource)
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-bfd(Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-0155(US Government Resource)
Weakness Type
CWE-388: 7PK - Errors
CWE-388 (7PK - Errors) is a weakness classification that describes the underlying vulnerability mechanism exploited in CVE-2018-0155. In this case, the weakness relates to how Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches handles input processing, leading to exploitable conditions.
Learn more: CWE-388 — 7PK - Errors
Impact Analysis
CVE-2018-0155 threatens the availability of Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches, as exploitation can cause process crashes, resulting in service disruption. With a CVSS score of 8.6 (HIGH) and a network-based attack vector requiring no authentication, the barrier to exploitation is low. The changed scope indicates that exploitation can affect resources beyond the vulnerable component, potentially impacting downstream network services and connected systems. In enterprise environments, repeated exploitation could cause sustained network outages affecting business operations, communications, and service availability. Network infrastructure devices are high-value targets, and their unavailability can have cascading effects across the organization.
Exploit Maturity
CVE-2018-0155 is listed in the CISA Known Exploited Vulnerabilities catalog, confirming that this vulnerability has been exploited in real-world attacks. The EPSS score of 11.22% (93.4rd percentile) places it among the most likely vulnerabilities to be exploited. Organizations should treat this vulnerability as an active and ongoing threat requiring immediate remediation.
Remediation
- Apply vendor updates immediately as required by CISA KEV: Apply updates per vendor instructions.
- If immediate patching is not possible, implement interim mitigations such as restricting access to the affected BFD feature to trusted networks only using access control lists.
- Monitor affected devices for signs of exploitation, including unexpected reloads, unusual network traffic, and anomalous process behavior.
- Ensure network monitoring and alerting is configured to detect denial-of-service conditions affecting the Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches infrastructure.
- Maintain up-to-date device configurations and backups to enable rapid recovery if exploitation causes device reloads.
Technical Details
CVE-2018-0155 is a denial-of-service vulnerability in the Bidirectional Forwarding Detection (BFD) offload implementation of Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches. The vulnerability allows an unauthenticated remote attacker to cause a process crash by sending specially crafted BFD packets. The CVSS v3.1 score of 8.6 reflects low attack complexity, no required privileges, and high impact on availability. The changed scope in the CVSS vector indicates that exploitation can impact resources beyond the vulnerable component itself.
Frequently Asked Questions
Is CVE-2018-0155 being actively exploited?
Yes. CVE-2018-0155 is listed in the CISA Known Exploited Vulnerabilities catalog, confirming active exploitation. The EPSS score of 11.22% (93.4rd percentile) further indicates a high likelihood of ongoing exploitation.
What products are affected by CVE-2018-0155?
CVE-2018-0155 affects Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches. Specifically, affected products include Cisco Ios, Cisco Ios Xe.
How do I fix CVE-2018-0155?
Apply updates per vendor instructions. If immediate patching is not feasible, apply interim mitigations such as access control restrictions and enhanced monitoring to detect exploitation attempts.
How severe is CVE-2018-0155?
CVE-2018-0155 has a CVSS score of 8.6 (HIGH). This is a high-severity denial-of-service vulnerability that can disrupt network operations. While it does not enable code execution, the availability impact on critical network infrastructure makes timely remediation essential.
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