CVE-2024-37886
📋 TL;DR
CVE-2024-37886 is a signature verification bypass vulnerability in Nextcloud's user_oidc app that allows attackers to potentially forge OpenID Connect authentication requests. This could lead to unauthorized access or account compromise. All Nextcloud instances using the user_oidc app before versions 1.3.5, 2.0.0, 3.0.0, 4.0.0, or 5.0.0 are affected.
💻 Affected Systems
- Nextcloud user_oidc app
📦 What is this software?
User Oidc by Nextcloud
⚠️ Risk & Real-World Impact
Worst Case
Attackers could gain unauthorized access to Nextcloud accounts, potentially compromising sensitive data or performing privilege escalation.
Likely Case
Authentication bypass allowing unauthorized access to user accounts via forged OpenID Connect requests.
If Mitigated
Limited impact with proper network segmentation and monitoring, but still presents authentication risk.
🎯 Exploit Status
Exploitation requires understanding of OpenID Connect protocol and ability to forge authentication requests.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.3.5, 2.0.0, 3.0.0, 4.0.0, or 5.0.0
Vendor Advisory: https://github.com/nextcloud/security-advisories/security/advisories/GHSA-vw5h-29xf-g55g
Restart Required: No
Instructions:
1. Access Nextcloud admin interface. 2. Navigate to Apps section. 3. Find 'user_oidc' app. 4. Update to version 1.3.5, 2.0.0, 3.0.0, 4.0.0, or 5.0.0. 5. Verify update completes successfully.
🔧 Temporary Workarounds
Disable user_oidc app
linuxTemporarily disable the vulnerable user_oidc app until patching is possible
occ app:disable user_oidc
🧯 If You Can't Patch
- Implement network-level controls to restrict access to Nextcloud authentication endpoints
- Enable enhanced logging and monitoring for authentication attempts and review regularly
🔍 How to Verify
Check if Vulnerable:
Check user_oidc app version in Nextcloud admin interface or run: occ app:list | grep user_oidcCheck Version:
occ app:list | grep user_oidcVerify Fix Applied:
Verify user_oidc app version shows 1.3.5, 2.0.0, 3.0.0, 4.0.0, or 5.0.0 in admin interface📡 Detection & Monitoring
Log Indicators:
- Unusual authentication patterns
- Failed OpenID Connect signature validations
- Authentication from unexpected sources
Network Indicators:
- Unusual traffic to /apps/user_oidc/ endpoints
- Authentication requests with modified signatures
SIEM Query:
source="nextcloud.log" AND ("user_oidc" OR "OpenID Connect") AND ("failed" OR "invalid" OR "signature")🔗 References
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-vw5h-29xf-g55g
- https://github.com/nextcloud/user_oidc/pull/715
- https://hackerone.com/reports/1878391
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-vw5h-29xf-g55g
- https://github.com/nextcloud/user_oidc/pull/715
- https://hackerone.com/reports/1878391
