CVE-2026-77093: Commvault Integer Overflow DOS Vulnerability

CVE-2026-77093 Overview

CVE-2026-77093 is an integer overflow vulnerability [CWE-190] in the Commvault CvFWD component. The flaw allows an authenticated remote attacker to disrupt service availability across Commvault deployments. Successful exploitation does not expose confidentiality or integrity but degrades the availability of affected services. Commvault published advisory CV_2026_10_2 directing customers to apply the resolved maintenance release across every Commvault role, including CommServe, Webserver, Command Center, MediaAgents, Clients, and HyperScale.

Critical Impact
An authenticated network-adjacent attacker can trigger an integer overflow in CvFWD to cause a denial-of-service condition against Commvault backup and recovery infrastructure.

Affected Products

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

Discovery Timeline

2026-10-13 - CVE-2026-77093 published to NVD
2026-10-14 - Last updated in NVD database

Technical Details for CVE-2026-77093

Vulnerability Analysis

The vulnerability resides in CvFWD, the Commvault firewall/forwarding daemon that mediates communication between Commvault roles. An integer overflow condition is reachable over the network by a user with low privileges and no user interaction. When the overflow is triggered, the affected service terminates or enters an unrecoverable state, interrupting backup, restore, and management workflows. Because CvFWD runs on nearly every Commvault role, the fault domain spans the entire deployment rather than a single host.

Root Cause

The underlying weakness is classified under CWE-190: Integer Overflow or Wraparound. A value derived from attacker-controlled input is used in an arithmetic operation without adequate bounds checking. The resulting wraparound produces an unexpected size or offset that drives downstream logic into an invalid state, crashing the CvFWD process.

Attack Vector

Exploitation requires network access to a Commvault service exposing CvFWD and valid low-privilege credentials. No user interaction is needed. The attacker sends a crafted message whose length or count field causes the overflow during parsing. The impact is limited to availability; the vulnerability does not permit code execution or data disclosure based on the published advisory. Refer to the Commvault Security Advisory CV_2026_10_2 for product-level details.

Detection Methods for CVE-2026-77093

Indicators of Compromise

Unexpected termination or repeated restarts of the CvFWD process on CommServe, MediaAgent, Webserver, or Client hosts.
Gaps or failures in scheduled backup, restore, or auxiliary copy jobs correlating with service outages.
Anomalous inbound traffic to Commvault service ports from accounts not previously communicating with those roles.

Detection Strategies

Monitor Commvault service logs for CvFWD crash events, stack traces, and abnormal exit codes.
Baseline authenticated session volume against Commvault services and alert on sudden spikes from a single source.
Correlate operating system event logs showing process termination of CvFWD with network connections preceding the crash.

Monitoring Recommendations

Enable centralized log forwarding from all Commvault roles to a SIEM for continuous availability monitoring.
Track job success rates and alert when backup or restore failure rates exceed historical thresholds.
Audit authenticated access to Commvault infrastructure and review accounts with network reachability to CvFWD endpoints.

How to Mitigate CVE-2026-77093

Immediate Actions Required

Inventory every Commvault role in the environment, including CommServe, Webserver, Command Center, MediaAgents, Clients, and HyperScale nodes.
Apply the resolved maintenance release referenced in Commvault advisory CV_2026_10_2 to all identified components.
Restrict network reachability of Commvault service ports to trusted management segments until patching is complete.

Patch Information

Commvault has published a resolved maintenance release addressing CVE-2026-77093. Customers should upgrade every Commvault installation per the vendor guidance in the Commvault Security Advisory CV_2026_10_2. Partial patching leaves cross-role communication exposed because CvFWD is present on all Commvault components.

Workarounds

Enforce network segmentation and firewall rules so only authorized Commvault hosts and administrators can reach CvFWD ports.
Rotate and restrict credentials for any low-privilege accounts able to authenticate to Commvault services.
Increase monitoring of Commvault service health and job status while patching is scheduled.

bash

# Example: restrict CvFWD exposure to a trusted management subnet (Linux iptables)
iptables -A INPUT -p tcp --dport 8400:8403 -s 10.10.20.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8400:8403 -j DROP