CVE-2025-21117
📋 TL;DR
Dell Avamar versions 19.4+ have an access token reuse vulnerability in the AUI (Avamar User Interface). A local attacker with low privileges could exploit this to fully impersonate legitimate users, potentially gaining unauthorized access to backup data and administrative functions. This affects all Dell Avamar installations running version 19.4 or later.
💻 Affected Systems
- Dell Avamar
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise where an attacker gains administrative privileges, accesses sensitive backup data, modifies backup policies, or disrupts backup operations across the entire Avamar environment.
Likely Case
Unauthorized access to backup data and administrative functions within the Avamar system, potentially leading to data exfiltration, backup corruption, or privilege escalation within the backup infrastructure.
If Mitigated
Limited impact due to proper network segmentation, strict access controls, and monitoring that would detect unusual authentication patterns or privilege escalation attempts.
🎯 Exploit Status
Exploitation requires local access to the Avamar system with any level of privileges. The vulnerability involves token reuse, which typically requires understanding of the authentication mechanism but doesn't require advanced technical skills.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply the security update referenced in DSA-2025-071
Vendor Advisory: https://www.dell.com/support/kbdoc/en-us/000281275/dsa-2025-071-security-update-for-dell-avamar-for-multiple-component-vulnerabilities
Restart Required: Yes
Instructions:
1. Review DSA-2025-071 advisory. 2. Download the appropriate security update from Dell Support. 3. Apply the update following Dell's documented procedures. 4. Restart Avamar services as required. 5. Verify the update was successful.
🔧 Temporary Workarounds
Restrict Local Access
allLimit local access to Avamar systems to only authorized administrators using strict access controls and monitoring.
Disable AUI if Not Required
allIf the Avamar User Interface is not required for operations, disable it to remove the attack surface.
🧯 If You Can't Patch
- Implement strict access controls to limit who can access Avamar systems locally
- Enable detailed authentication logging and monitor for unusual token usage patterns
🔍 How to Verify
Check if Vulnerable:
Check Avamar version using 'avmgr version' command and verify if it's 19.4 or later with AUI enabled.Check Version:
avmgr versionVerify Fix Applied:
Verify the security update from DSA-2025-071 has been applied and check that the vulnerability no longer exists through testing or vendor verification.📡 Detection & Monitoring
Log Indicators:
- Multiple authentication attempts from same user in short time
- Unusual privilege escalation patterns
- Access token reuse patterns in authentication logs
Network Indicators:
- Unusual authentication traffic to Avamar AUI
- Multiple session creations from single source
SIEM Query:
source="avamar_logs" AND (event_type="authentication" OR event_type="token_validation") AND (user_privilege_change="true" OR token_reuse="detected")