1. Introduction
CiscoWorks Common Services HTTP Response Splitting is a vulnerability affecting Cisco network management software. It allows a remote attacker to inject malicious headers into HTTP responses, potentially leading to modification of web page content or redirection to untrusted sites. This affects systems running vulnerable versions of CiscoWorks Common Services and could compromise the confidentiality, integrity, and availability of affected services.
2. Technical Explanation
The vulnerability stems from insufficient input validation in the ‘URL’ parameter of Autologin.jsp within CiscoWorks Common Services. An attacker can craft a malicious URL containing HTTP header injections that are then reflected back to the user’s browser. This allows them to control parts of the HTTP response, potentially leading to cross-site scripting (XSS) or other attacks. The vulnerability is tracked as CVE-2011-4237 and has a CWE score of 20 (Improper Input Validation).
- Root cause: Missing input validation on the ‘URL’ parameter in Autologin.jsp allows arbitrary HTTP header injection.
- Exploit mechanism: An attacker crafts a malicious URL with injected headers and tricks a user into visiting it, causing their browser to interpret the injected content. For example, an attacker could inject a redirect header to send the user to a phishing site.
- Scope: CiscoWorks Common Services versions prior to those containing fixes for CSCtt34638, CSCtu18693, CSCtx59431, CSCtx59438, CSCtx59447 and CSCtx59451 are affected.
3. Detection and Assessment
- Quick checks: Use the Cisco software show command-line interface (CLI) to display installed versions.
- Scanning: Nessus plugins 9a4f1b73, 4da1bafd, 46462822, 3749073d and af05872e can detect this vulnerability (example only).
- Logs and evidence: Examine web server logs for requests to Autologin.jsp containing suspicious characters in the ‘URL’ parameter.
4. Solution / Remediation Steps
4.1 Preparation
- Back up your CiscoWorks Common Services configuration and web server data. Stop affected services if possible, but note potential service disruption.
- Ensure a roll back plan is in place by keeping the original software version available for re-installation.
- A change window may be required depending on business impact; approval from relevant stakeholders might be needed.
4.2 Implementation
- Step 1: Download and install the latest patch or upgrade package from Cisco’s website, addressing CSCtt34638, CSCtu18693, CSCtx59431, CSCtx59438, CSCtx59447 and CSCtx59451.
- Step 2: Restart the affected CiscoWorks Common Services services to apply the changes.
4.3 Config or Code Example
Before
After
4.4 Security Practices Relevant to This Vulnerability
Several security practices can help prevent this type of vulnerability. Input validation is crucial for blocking malicious data, while least privilege limits the impact if an attacker gains control. A regular patch cadence ensures timely application of security fixes.
- Practice 1: Implement strict input validation on all user-supplied data to prevent injection attacks.
- Practice 2: Apply the principle of least privilege to limit the permissions of affected services and users.
4.5 Automation (Optional)
5. Verification / Validation
Confirm that the fix has been applied by checking the updated version of CiscoWorks Common Services and re-testing for the vulnerability. Perform a basic service smoke test to ensure functionality remains intact.
- Post-fix check: Use the Cisco software show command-line interface (CLI) to verify the installed version is patched.
- Smoke test: Verify basic functionality of CiscoWorks Common Services, such as device discovery and monitoring.
- Monitoring: Monitor web server logs for any suspicious activity related to Autologin.jsp (example only).
6. Preventive Measures and Monitoring
Update security baselines to include the latest CiscoWorks Common Services version. Incorporate vulnerability scanning into CI/CD pipelines to detect similar issues early in the development process. Establish a regular patch review cycle to ensure timely application of security updates.
- Baselines: Update your security baseline or policy to require patched versions of CiscoWorks Common Services.
- Pipelines: Add static analysis (SAST) and dynamic analysis (DAST) tools to your CI/CD pipeline to identify potential input validation issues.
- Asset and patch process: Implement a regular patch review cycle, such as monthly or quarterly, to ensure timely application of security updates.
7. Risks, Side Effects, and Roll Back
Applying patches may cause temporary service disruption. Always test in a non-production environment first. If issues arise, roll back by restoring the previous software version and configuration.
- Risk or side effect 1: Patch installation could lead to brief service downtime; plan accordingly.
- Roll back: Restore the previous version of CiscoWorks Common Services and its configuration from your backup. Restart affected services.
8. References and Resources
- Vendor advisory or bulletin: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120118-common
- NVD or CVE entry: https://nvd.nist.gov/vuln/detail/CVE-2011-4237
- Product or platform documentation relevant to the fix: https://www.cisco.com/c/en/us/support/unified-communications/works-common-services/tsd-products-support