CVE-2026-76980: ManageEngine Data Exposure Vulnerability

CVE-2026-76980 Overview

CVE-2026-76980 is a data exposure vulnerability affecting ZohoCorp ManageEngine OpManager and Firewall Analyzer versions 12.8.709 and below. The flaw resides in the Firewall Analyzer syslog collector, which processes inbound syslog messages from network devices. An attacker positioned on an adjacent network can exploit the weakness to access sensitive information without authentication or user interaction. The vulnerability is categorized under [CWE-20] Improper Input Validation and carries a scope-changed confidentiality impact.

Critical Impact

An unauthenticated attacker on an adjacent network can extract sensitive data from the Firewall Analyzer syslog collector, exposing information beyond the vulnerable component's trust boundary.

Affected Products

• ZohoCorp ManageEngine OpManager versions 12.8.709 and below
• ZohoCorp ManageEngine Firewall Analyzer versions 12.8.709 and below
• Firewall Analyzer syslog collector component

Discovery Timeline

• 2026-09-23 - CVE-2026-76980 published to NVD
• 2026-09-23 - Last updated in NVD database

Technical Details for CVE-2026-76980

Vulnerability Analysis

The vulnerability exists within the syslog collector service in ManageEngine Firewall Analyzer, a component that is also embedded in ManageEngine OpManager. The syslog collector ingests log messages from firewalls and network devices over standard syslog transports. Improper input validation in this listener allows an attacker to trigger disclosure of data that should remain protected within the application boundary. Because the scope is changed, the disclosed data can include information belonging to components outside the syslog collector itself.

Root Cause

The root cause is improper input validation ([CWE-20]) in the syslog message parsing path. The collector does not adequately validate incoming syslog payloads before processing them, allowing crafted messages to influence subsequent read or serialization operations. This behavior enables an adjacent attacker to obtain sensitive data without altering system integrity or availability.

Attack Vector

Exploitation requires network adjacency, meaning the attacker must reside on the same broadcast domain or a logically adjacent segment where syslog traffic to the collector is reachable. No authentication or user interaction is required. An attacker sends crafted syslog messages to the Firewall Analyzer collector to trigger the data exposure condition. See the ManageEngine Security Advisory CVE-2026-76980 for vendor-provided technical context.

Detection Methods for CVE-2026-76980

Indicators of Compromise

• Unexpected or malformed syslog packets directed at the Firewall Analyzer collector port from non-authorized network devices.
• Outbound data flows from the ManageEngine host that correlate with inbound syslog activity from untrusted sources.
• Log entries in Firewall Analyzer showing parsing errors or anomalous message structures immediately preceding suspicious application behavior.

Detection Strategies

• Inspect syslog traffic on the Firewall Analyzer listener for messages originating from IP addresses outside the documented set of managed firewalls and network devices.
• Baseline the volume and format of syslog messages processed by the collector and alert on statistical deviations.
• Review ManageEngine application and access logs for unauthorized retrievals of configuration or log data shortly after abnormal syslog activity.

Monitoring Recommendations

• Forward Firewall Analyzer and OpManager application logs to a centralized analytics platform for correlation with network telemetry.
• Monitor firewall counters on UDP/TCP 514 and any custom syslog ports for traffic sourced from unauthorized VLANs or subnets.
• Track process behavior on the ManageEngine host to detect unusual file reads or network egress originating from the syslog collector process.

How to Mitigate CVE-2026-76980

Immediate Actions Required

• Upgrade ManageEngine OpManager and Firewall Analyzer to a version above 12.8.709 as directed in the vendor advisory.
• Restrict network access to the syslog collector so only authorized firewalls and network devices can reach the listening port.
• Audit the current syslog source list and remove any devices no longer required to send data to the collector.

Patch Information

ZohoCorp addresses CVE-2026-76980 in ManageEngine OpManager and Firewall Analyzer builds released after 12.8.709. Consult the ManageEngine Security Advisory CVE-2026-76980 for the specific fixed build number and upgrade instructions applicable to your deployment.

Workarounds

• Segment the ManageEngine server into a dedicated management VLAN and enforce access control lists that permit syslog traffic only from known device IPs.
• Place a firewall or packet filter in front of the syslog collector to drop malformed or oversized syslog packets before they reach the application.
• Disable the Firewall Analyzer syslog collector service if it is not actively used until the patched version is deployed.

# Example ACL restricting syslog to authorized device subnets
iptables -A INPUT -p udp --dport 514 -s 10.10.20.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 514 -s 10.10.20.0/24 -j ACCEPT
iptables -A INPUT -p udp --dport 514 -j DROP
iptables -A INPUT -p tcp --dport 514 -j DROP