CVE-2026-77094: CvFWD Out-of-Bounds Write DoS Vulnerability

CVE-2026-77094 Overview

CVE-2026-77094 is an out-of-bounds write vulnerability [CWE-787] in the Commvault CvFWD component. The flaw affects service availability and can be triggered by an authenticated attacker over the network. Commvault addressed the issue in a maintenance release and advises customers to update all Commvault installations, including CommServe, Webserver, Command Center, MediaAgents, Clients, and HyperScale.

Critical Impact
Successful exploitation causes a denial-of-service condition in CvFWD, disrupting Commvault data protection services across the environment.

Affected Products

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

Discovery Timeline

2026-10-13 - CVE-2026-77094 published to NVD
2026-10-14 - Last updated in NVD database

Technical Details for CVE-2026-77094

Vulnerability Analysis

The vulnerability resides in CvFWD, a Commvault service component involved in internal communications across the data protection fabric. An authenticated remote attacker can send crafted input that causes CvFWD to write data beyond the bounds of an allocated buffer. The resulting memory corruption disrupts the service and produces a denial-of-service condition.

The weakness is classified as an out-of-bounds write [CWE-787]. Exploitation targets availability only; confidentiality and integrity are not affected according to the published CVSS vector. Because CvFWD participates in communication between Commvault roles such as CommServe, MediaAgents, and Clients, loss of the service interrupts backup and recovery workflows across the environment.

Root Cause

The root cause is improper bounds checking when CvFWD processes attacker-supplied data. The component writes past the end of a fixed-size memory region, corrupting adjacent memory and terminating the process. Specific implementation details are not published in the vendor advisory.

Attack Vector

The attack vector is network-based and requires low privileges with no user interaction. An authenticated attacker who can reach the CvFWD service on a Commvault host can trigger the fault remotely. Refer to the Commvault Security Advisory CV_2026_10_1 for technical specifics.

No verified public exploit code is available at the time of writing.

Detection Methods for CVE-2026-77094

Indicators of Compromise

Unexpected crashes or restarts of the CvFWD process on CommServe, MediaAgents, Webserver, Command Center, Clients, or HyperScale nodes.
Repeated or malformed network traffic directed at CvFWD listening ports from unexpected sources.
Failed or incomplete backup, restore, or replication jobs correlating with CvFWD service interruptions.

Detection Strategies

Monitor Commvault service logs and the Windows or Linux event logs for abnormal termination of CvFWD.
Alert on spikes in connection errors or protocol parsing errors reported by CvFWD.
Correlate job failures in the CommServe database with host-level service availability metrics.

Monitoring Recommendations

Centralize Commvault logs into a SIEM or data lake and build availability dashboards for CvFWD.
Baseline normal client-to-MediaAgent traffic patterns and alert on deviations.
Track patch state across all Commvault roles to confirm complete remediation coverage.

How to Mitigate CVE-2026-77094

Immediate Actions Required

Inventory every Commvault role in the environment, including CommServe, Webserver, Command Center, MediaAgents, Clients, and HyperScale.
Apply the Commvault maintenance release that resolves CVE-2026-77094 to all identified hosts.
Restrict network access to Commvault service ports so only trusted management networks can reach CvFWD.

Patch Information

Commvault published fixes in a maintenance release described in Commvault Security Advisory CV_2026_10_1. Customers must upgrade all Commvault installations to the resolved maintenance release to remediate the vulnerability.

Workarounds

Limit exposure of CvFWD listening ports using host firewalls and network segmentation until patches are deployed.
Enforce least-privilege access for Commvault service accounts to reduce the pool of authenticated users who can reach the service.
Monitor CvFWD process health and automate restart with alerting while remediation is in progress.

bash

# Example: restrict CvFWD access to a trusted management subnet (Linux, illustrative)
# Replace 10.10.0.0/24 and <CvFWD_PORT> with values appropriate to your deployment
iptables -A INPUT -p tcp --dport <CvFWD_PORT> -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport <CvFWD_PORT> -j DROP