CVE-2026-77105: 
Commvault vulnerability analysis and mitigation

CVE-2026-77105 is a cryptographic signature verification flaw in Commvault's CommServe component that allows authenticated low-privileged users to bypass privilege management controls and perform high-privilege operations. The vulnerability was published on September 8, 2026, and affects Commvault Cloud versions 11.36.0–11.36.122, 11.40.0–11.40.71, 11.44.0–11.44.19, and 11.46.0–11.46.19. It carries a CVSS v3.1 base score of 8.8 (High) and a CVSS v4.0 base score of 8.7 (High) (GitHub Advisory, Commvault Advisory).

The root cause is classified as CWE-347 (Improper Verification of Cryptographic Signature), where CommServe fails to properly verify cryptographic signatures used in privilege management decisions. An authenticated attacker with low privileges can exploit this flaw over the network — without user interaction or special conditions — to bypass authorization checks and invoke operations reserved for high-privileged accounts. The attack vector is network-accessible, attack complexity is low, and no additional attack requirements exist, making exploitation straightforward for any authenticated user. The vulnerability is also mapped to CAPEC-475 (Signature Spoofing by Improper Validation) (GitHub Advisory, Commvault Advisory).

Successful exploitation allows a low-privileged authenticated attacker to read sensitive data, modify CommServe system configuration and data, and disrupt CommServe availability — resulting in full confidentiality, integrity, and availability compromise of the affected system. Because CommServe is the central management server for Commvault backup and data protection infrastructure, compromise could expose backup data, credentials, and configuration details for all managed systems, with significant potential for lateral movement across the enterprise. The CVSS v4.0 assessment confirms high impact across all three security pillars for the vulnerable system (GitHub Advisory, Commvault Advisory).

There is no public proof-of-concept exploit and no evidence of in-the-wild exploitation as of the time of publication (GitHub Advisory). The EPSS score is approximately 0.152–0.177%, placing it in a low percentile for near-term exploitation probability. No threat actor attribution has been reported, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. The NVD SSVC assessment classifies exploitation as "none" and the vulnerability as not automatable (Commvault Advisory).

1. Reconnaissance: Identify Commvault CommServe instances exposed on the network, targeting versions within the affected ranges (11.36.0–11.36.122, 11.40.0–11.40.71, 11.44.0–11.44.19, 11.46.0–11.46.19) using network scanning or service fingerprinting tools.
2. Obtain low-privileged credentials: Acquire valid CommServe credentials with minimal privileges — these may be obtained via phishing, credential reuse, or a free/trial account if available.
3. Authenticate to CommServe: Log in to the CommServe or Web Server interface using the low-privileged account.
4. Craft malicious request: Construct an API or protocol-level request that invokes a privileged operation, supplying a forged or improperly validated cryptographic signature that CommServe fails to reject due to the verification flaw.
5. Bypass privilege check: CommServe accepts the malformed signature and grants the request elevated privileges, allowing the attacker to execute administrative operations, access sensitive backup data, or modify system configuration.
6. Achieve objective: Leverage elevated access to exfiltrate sensitive data, alter backup configurations, disrupt availability, or pivot to other systems managed by CommServe (GitHub Advisory, Commvault Advisory).

• Logs: CommServe audit logs showing low-privileged accounts performing administrative or high-privilege operations (e.g., configuration changes, backup policy modifications, user management) without corresponding authorization events.
• Logs: Unexpected privilege escalation events or authorization errors followed by successful privileged API calls in CommServe or Web Server logs.
• Network: Unusual API requests to CommServe endpoints from accounts not normally associated with administrative activity; requests with anomalous or malformed signature fields.
• File System: Unexpected changes to CommServe configuration files or backup policies not initiated by known administrators.
• Process: Unusual administrative tasks or scheduled jobs created under low-privileged service accounts on the CommServe host (Commvault Advisory).

Commvault has released patched maintenance releases addressing this vulnerability. Customers should upgrade CommServe and Web Server to the following fixed versions: 11.36.123 or later (11.36.x branch), 11.40.72 or later (11.40.x branch), 11.44.20 or later (11.44.x branch), or 11.46.20 or later (11.46.x branch). As an interim measure, restrict network access to CommServe to trusted networks only, and monitor CommServe logs for unauthorized privilege escalation attempts. Upgrading both CommServe and Web Server components is required (Commvault Advisory, GitHub Advisory).