Full Report
Drupal security advisory (AV26-738)
Analysis Summary
# Vulnerability: Internationalization Single Sign-On Access Bypass
## CVE Details
- **CVE ID:** Pending / Not explicitly listed in advisory (Referenced via SA-CONTRIB-2026-081)
- **CVSS Score:** 9.0 - 10.0 (Estimated based on "Critical" rating)
- **CWE:** CWE-284 (Improper Access Control) / CWE-285 (Improper Authorization)
## Affected Systems
- **Products:** Drupal Contributed Module: Internationalization Single Sign-On (i18n_sso)
- **Versions:** All versions prior to 1.8.0
- **Configurations:** Systems utilizing this module to handle authentication and session synchronization across multiple domains or localized sites.
## Vulnerability Description
A critical access bypass vulnerability exists in the Internationalization Single Sign-On module. The flaw allows an unauthenticated attacker to bypass security restrictions and potentially gain unauthorized access to user sessions or administrative interfaces. The technical nature of the flaw involves a failure in the module's logic when validating authentication tokens or session data across disparate localized domains.
## Exploitation
- **Status:** Not currently reported as exploited in the wild; PoC typically follows disclosure of Drupal Contrib advisories.
- **Complexity:** Low
- **Attack Vector:** Network (Remote)
## Impact
- **Confidentiality:** High (Potential access to sensitive user data)
- **Integrity:** High (Potential to perform actions as other users)
- **Availability:** Low
## Remediation
### Patches
The Drupal security team recommends upgrading to the following version immediately:
- **Internationalization Single Sign-On 1.8.0**
### Workarounds
- Disable the **Internationalization Single Sign-On (i18n_sso)** module until the update can be applied.
- Restrict access to the site via firewall or maintenance mode if patching is not immediately possible.
## Detection
- **Indicators of Compromise:** Monitor logs for unusual authentication patterns, specifically requests to SSO callback URLs from unexpected IP addresses or session hijacking attempts.
- **Detection methods and tools:** Audit Drupal site logs for "access denied" errors followed by successful logins from the same session ID across different domain prefixes.
## References
- **Vendor Advisory:** hxxps[://]www[.]drupal[.]org/sa-contrib-2026-081
- **Drupal Security Home:** hxxps[://]www[.]drupal[.]org/security
- **Cyber Centre Advisory:** hxxps[://]www[.]cyber[.]gc[.]ca/en/alerts-advisories/drupal-security-advisory-av26-738