CVE-2026-27949 Overview
Plane is an open-source project management tool that contains an Information Exposure vulnerability in its authentication flow. Prior to version 1.3.0, a security flaw was identified where a user's email address is included as a query parameter in the URL during error handling scenarios, such as when an invalid magic code is submitted during authentication. This practice of transmitting personally identifiable information (PII) via GET request query strings represents an insecure design pattern that can lead to unintended data exposure.
Critical Impact
User email addresses may be exposed through browser history, server logs, referrer headers, and shared URLs when authentication errors occur.
Affected Products
- Plane versions prior to 1.3.0
- Authentication utility module (packages/utils/src/auth.ts)
Discovery Timeline
- 2026-04-07 - CVE-2026-27949 published to NVD
- 2026-04-08 - Last updated in NVD database
Technical Details for CVE-2026-27949
Vulnerability Analysis
This vulnerability falls under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor). The flaw exists within Plane's authentication utility module located at packages/utils/src/auth.ts. When a user submits an invalid magic code during the authentication process, the application's error handling logic redirects the user to an error page while including their email address as a query parameter in the URL.
This design approach violates security best practices because GET request parameters are inherently insecure for transmitting sensitive information. Unlike POST request bodies, URL query parameters are visible in multiple locations and can persist in various logs and caches.
Root Cause
The root cause of this vulnerability is an insecure design decision in the error handling path of the authentication flow. Rather than storing error context in server-side session state or using secure POST redirects, the application appends the user's email address directly to the redirect URL as a query parameter. This pattern was present in the authentication utility module before the fix was implemented in version 1.3.0.
Attack Vector
The vulnerability requires network access and user interaction to exploit. An attacker could potentially harvest email addresses through several vectors:
Browser History Exposure: Any user who authenticates on a shared computer leaves their email address in the browser history if they encounter an authentication error.
Server Log Harvesting: Web servers, proxies, and CDNs routinely log full URLs including query parameters. An attacker with access to these logs could extract email addresses.
Referrer Header Leakage: If the error page contains links to external resources, the email-containing URL may be transmitted in HTTP Referer headers to third-party services.
Shoulder Surfing: The email address is visible in the browser's address bar, making it susceptible to visual observation.
For detailed technical information, see the GitHub Security Advisory.
Detection Methods for CVE-2026-27949
Indicators of Compromise
- Presence of email addresses in web server access logs within URL query parameters for authentication-related endpoints
- Browser history entries containing user email addresses in authentication error URLs
- Referrer header logs from third-party services showing email addresses from your Plane instance
Detection Strategies
- Review web server access logs for authentication endpoints containing email patterns in query strings (e.g., ?email= or URL-encoded @ symbols)
- Implement log analysis to flag any PII appearing in URL paths or query parameters
- Monitor network traffic for authentication redirects that include email addresses in the URL
Monitoring Recommendations
- Configure web application firewalls to alert on PII patterns in URL query strings
- Set up log monitoring rules to detect email address patterns in access logs
- Review CDN and proxy logs for instances where email addresses may have been cached or logged
How to Mitigate CVE-2026-27949
Immediate Actions Required
- Upgrade Plane to version 1.3.0 or later immediately
- Review and purge server logs, proxy logs, and CDN caches that may contain exposed email addresses
- Clear browser history on shared workstations that have accessed the Plane authentication flow
Patch Information
This vulnerability is fixed in Plane version 1.3.0. The fix addresses the insecure practice of transmitting email addresses via URL query parameters during authentication error handling. Organizations should upgrade to version 1.3.0 or later to remediate this vulnerability. For additional details, refer to the GitHub Security Advisory.
Workarounds
- If immediate upgrade is not possible, consider temporarily disabling magic code authentication and using alternative authentication methods
- Implement a reverse proxy rule to strip or redact email parameters from authentication URLs before logging
- Configure web servers to exclude authentication endpoints from access logging until the upgrade can be completed
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
