CVE-2025-21120 is a vulnerability identified in Dell Avamar Server, specifically affecting versions 19.8 through 19.10 prior to the application of patch 338904. The root cause is related to the server's improper trust in HTTP permission methods, classified under CWE-650, which involves trusting client-supplied HTTP methods for permission decisions on the server side. This flaw allows a low-privileged attacker with remote network access to manipulate HTTP methods to bypass intended permission checks. Because the server incorrectly trusts these HTTP methods, the attacker can potentially access sensitive information that should be restricted, leading to information disclosure. The vulnerability does not require user interaction and can be exploited remotely, increasing its risk profile. The CVSS v3.1 base score of 8.3 indicates high severity, with attack vector being network (AV:N), low attack complexity (AC:L), requiring low privileges (PR:L), no user interaction (UI:N), unchanged scope (S:U), and high impact on confidentiality and integrity (C:H/I:H) with low impact on availability (A:L). Although no exploits are currently known in the wild, the vulnerability poses a significant risk to organizations relying on affected Dell Avamar Server versions for backup and recovery operations.

The exploitation of CVE-2025-21120 can lead to unauthorized disclosure of sensitive information stored or processed by Dell Avamar Server. This can compromise the confidentiality and integrity of backup data, potentially exposing critical business information, intellectual property, or personal data. Since Avamar is widely used for enterprise backup and recovery, attackers gaining access to this information could leverage it for further attacks, including ransomware or data theft campaigns. The low complexity and remote exploitability increase the likelihood of attacks, especially in environments where network access controls are insufficient. Although availability impact is low, the breach of confidentiality and integrity can have severe operational and reputational consequences. Organizations in sectors such as finance, healthcare, government, and large enterprises that rely heavily on Avamar for data protection are particularly vulnerable. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, as attackers may develop exploits rapidly once details are public.

To mitigate CVE-2025-21120, organizations should immediately apply the official patch 338904 provided by Dell for Avamar Server versions 19.8 through 19.10. Until patching is complete, implement strict network segmentation and firewall rules to restrict access to Avamar Server management interfaces to trusted administrative networks only. Employ strong authentication and authorization controls to limit low-privileged user access. Monitor network traffic for unusual HTTP methods or anomalous access patterns targeting Avamar servers. Conduct regular audits of server configurations to ensure HTTP methods are validated server-side and not blindly trusted. Additionally, consider deploying Web Application Firewalls (WAFs) with custom rules to block suspicious HTTP methods or malformed requests. Educate IT and security teams about this vulnerability to ensure rapid detection and response. Finally, maintain up-to-date backups and incident response plans to minimize impact if exploitation occurs.