CVE-2026-77095: Commvault CvFWD DOS Vulnerability

CVE-2026-77095 Overview

CVE-2026-77095 is a null pointer dereference vulnerability [CWE-476] in the Commvault CvFWD service. The flaw allows an authenticated attacker with low privileges to disrupt service availability over the network. Commvault published Security Advisory CV_2026_10_5 directing customers to upgrade to a resolved maintenance release across all Commvault components, including CommServe, Webserver, Command Center, MediaAgents, Clients, and HyperScale deployments.

Critical Impact
An authenticated remote attacker can trigger a null pointer dereference in CvFWD, causing a denial-of-service condition that disrupts backup, recovery, and data protection operations across the Commvault environment.

Affected Products

Commvault CommServe and Webserver
Commvault Command Center and MediaAgents
Commvault Clients and HyperScale appliances

Discovery Timeline

2026-10-13 - CVE-2026-77095 published to the National Vulnerability Database (NVD)
2026-10-14 - Last updated in NVD database

Technical Details for CVE-2026-77095

Vulnerability Analysis

The vulnerability resides in CvFWD, the Commvault forwarding service that mediates network communications between Commvault components. A null pointer dereference [CWE-476] occurs when the service dereferences a pointer that has not been initialized or has been set to null during request processing. The resulting access violation terminates the service process, interrupting backup, restore, and replication workflows that depend on CvFWD connectivity.

Because Commvault serves as the data protection control plane, loss of CvFWD availability can cascade into failed backup windows, broken recovery objectives, and disrupted MediaAgent coordination. The flaw affects confidentiality and integrity neither of data at rest nor data in transit, but it does disrupt the availability of core data protection services.

Root Cause

The root cause is improper validation of a pointer prior to dereference within CvFWD request handling logic. When a crafted or unexpected input is processed, the service fails to verify that the pointer references a valid object, leading to a crash. Commvault's advisory CV_2026_10_5 identifies the condition as a null pointer dereference affecting service availability.

Attack Vector

Exploitation requires network access to the CvFWD service and low-level authenticated privileges on the Commvault environment. An attacker with valid credentials can send a specially shaped request to trigger the dereference. No user interaction is required. Public proof-of-concept code is not available at this time, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Technical specifics beyond the advisory are not published. Refer to the Commvault Security Advisory CV_2026_10_5 for authoritative details.

Detection Methods for CVE-2026-77095

Indicators of Compromise

Unexpected termination or repeated restarts of the CvFWD service process on CommServe, MediaAgent, or Client hosts
Crash dump files or Windows Application event log entries referencing CvFWD.exe access violations
Gaps in backup job completion correlated with CvFWD service outages

Detection Strategies

Monitor Commvault service health telemetry for abnormal CvFWD restart counts or faulting module events
Correlate authenticated session logs with service crashes to identify the source account triggering the condition
Alert on repeated network connections to Commvault service ports followed by immediate service termination

Monitoring Recommendations

Forward Commvault logs, Windows Event Logs, and Linux syslog to a centralized SIEM for correlation
Establish baselines for CvFWD uptime and alert on deviations exceeding normal operational variance
Track authentication events against Commvault consoles to identify anomalous low-privilege account usage

How to Mitigate CVE-2026-77095

Immediate Actions Required

Inventory all Commvault components, including CommServe, Webserver, Command Center, MediaAgents, Clients, and HyperScale appliances
Apply the resolved maintenance release referenced in Commvault Security Advisory CV_2026_10_5 to every component
Restrict network access to Commvault service ports to trusted management networks only
Review and prune low-privilege Commvault accounts to minimize the authenticated attack surface

Patch Information

Commvault has published fixed maintenance releases. Customers must upgrade every Commvault installation, including CommServe, Webserver, Command Center, MediaAgents, Clients, and HyperScale. Consult the Commvault Security Advisory CV_2026_10_5 for the specific resolved release numbers that apply to your deployment.

Workarounds

Place Commvault management interfaces behind network segmentation and firewall ACLs that limit source IPs
Enforce least privilege on Commvault role assignments and rotate credentials for low-privilege accounts
Enable service auto-restart with alerting so that CvFWD outages are detected and remediated quickly while patching is scheduled

bash

# Example: restrict access to Commvault service ports using iptables
# Replace 10.0.0.0/24 with your trusted management subnet
iptables -A INPUT -p tcp --dport 8400:8403 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8400:8403 -j DROP