How to remediate – Web Application Cookies Are Expired

1. Introduction

HTTP cookies have an ‘Expires’ attribute set with a past date or time in this vulnerability, meaning they are removed by the browser. This can disrupt application functionality that relies on these cookies for session management or user preferences. Web applications using cookies across various platforms and frameworks are usually affected. A likely impact is reduced availability of features dependent on those cookies, with low risk to confidentiality and integrity.

2. Technical Explanation

The web application sets cookies that include an ‘Expires’ attribute in the past. Browsers interpret this as a signal to delete the cookie immediately. This means any data stored within the cookie is lost, potentially breaking user sessions or requiring re-authentication. An attacker doesn’t directly exploit this; it’s a configuration issue causing unintended behaviour. For example, if an application relies on a specific cookie for remembering a shopping cart, that cart will be emptied when the browser removes the expired cookie.

• Root cause: Incorrectly configured ‘Expires’ attribute in HTTP cookies.
• Exploit mechanism: An attacker does not actively exploit this issue. The vulnerability manifests as lost session data or broken functionality due to the browser removing the cookie.
• Scope: Web applications using any server-side technology (e.g., Java, PHP, Python, .NET) that sets cookies with past expiration dates.

3. Detection and Assessment

Confirming this vulnerability involves checking cookie headers in browser developer tools or using a network proxy. A thorough method is to scan the application’s responses for expired cookies.

• Quick checks: Use your browser’s developer tools (usually F12) to inspect the HTTP response headers when interacting with the web application. Look at the ‘Set-Cookie’ header and check the ‘Expires’ attribute of each cookie.
• Scanning: Nessus detected this vulnerability, indicating a potential issue. Other scanners may have similar checks for expired cookies.
• Logs and evidence: Web server logs might show requests setting cookies with past expiration dates, but direct inspection of headers is more reliable.

curl -v https://example.com

4. Solution / Remediation Steps

Fixing this issue requires reviewing each cookie and either extending its expiration date or removing the ‘Expires’ attribute to make it a session cookie.

4.1 Preparation

• Ensure you have access to modify the application’s code or configuration files. A roll back plan involves restoring the original configuration file.
• Change windows should be planned during off-peak hours and approved by a senior administrator.

4.2 Implementation

1. Step 1: Identify all cookies set by the application.
2. Step 2: Review each cookie to determine if it contains sensitive data or is relied upon for security decisions.
3. Step 3: For cookies that need to persist, update the ‘Expires’ attribute with a future date and time.
4. Step 4: For cookies that do not need to persist beyond the current session, remove the ‘Expires’ attribute altogether.
5. Step 5: Restart the web application or relevant services if required for changes to take effect.

4.3 Config or Code Example

Before

Set-Cookie: myCookie=value; Expires=Wed, 21 Oct 2023 07:28:00 GMT

After

Set-Cookie: myCookie=value; Max-Age=3600  // Session cookie with a lifetime of one hour. Or... Set-Cookie: myCookie=value; Expires=Thu, 01 Jan 2025 00:00:00 GMT // Cookie expires in the future

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this issue.

• Practice 1: Secure defaults – configure cookies with appropriate expiration times or session-only settings by default.
• Practice 2: Input validation – ensure that any data stored in cookies is properly validated to prevent injection attacks.

4.5 Automation (Optional)

Automation may be possible using scripting languages to modify configuration files, but requires careful testing.

# Example PowerShell script (use with caution!)
# Get-Content -Path "C:pathtoconfig.ini" | ForEach-Object { $_ -replace 'Expires=.*?;', '' } | Set-Content -Path "C:pathtoconfig.ini"

5. Verification / Validation

• Post-fix check: Use your browser’s developer tools to inspect the ‘Set-Cookie’ header. Verify that all cookies either have a future ‘Expires’ attribute or lack an ‘Expires’ attribute altogether.
• Re-test: Re-run the curl command from the detection phase and confirm that no expired cookies are returned.
• Smoke test: Log in to the application and verify that your session is maintained as expected. Test key functionality dependent on cookies, such as shopping cart persistence.
• Monitoring: Monitor web server logs for any errors related to cookie handling or session management.

curl -v https://example.com

6. Preventive Measures and Monitoring

Updating security baselines and incorporating checks into CI/CD pipelines can help prevent this issue.

• Baselines: Update your web application security baseline to include a requirement for valid cookie expiration times or session-only cookies.
• Pipelines: Add static analysis tools (SAST) to your CI/CD pipeline to scan code for incorrectly configured cookies.
• Asset and patch process: Regularly review web application configurations as part of your asset management process.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Extending expiration dates too far could increase the risk of session hijacking.
• Risk or side effect 2: Removing ‘Expires’ attributes from cookies that require persistence will cause data loss.
• Roll back: Restore the original configuration file and restart the web application or relevant services.

8. References and Resources

• Vendor advisory or bulletin: No specific vendor advisory available, as this is a general configuration issue.
• NVD or CVE entry: No specific CVE entry exists for this broad issue.
• Product or platform documentation relevant to the fix: https://tools.ietf.org/html/rfc6265