CVE-2026-48923: Jenkins AppSpider Plugin Auth Bypass Flaw

CVE-2026-48923 Overview

CVE-2026-48923 affects the Jenkins AppSpider Plugin version 1.0.17 and earlier. The plugin fails to perform a permission check in a method that implements form validation. Attackers holding Overall/Read permission can abuse this flaw to make the Jenkins controller connect to an attacker-specified URL.

The issue is classified under [CWE-269] Improper Privilege Management. It enables a low-privileged authenticated user to trigger outbound HTTP requests from the Jenkins server, which can be used for internal reconnaissance or to interact with internal-only services.

Critical Impact
Authenticated users with minimal Overall/Read access can force the Jenkins controller to issue HTTP requests to arbitrary attacker-controlled URLs, exposing internal services and enabling server-side request forgery style behavior.

Affected Products

Jenkins AppSpider Plugin 1.0.17
Jenkins AppSpider Plugin versions prior to 1.0.17
Jenkins controllers with the AppSpider Plugin installed and enabled

Discovery Timeline

2026-05-27 - CVE-2026-48923 published to NVD via Jenkins Security Advisory SECURITY-3671
2026-05-27 - Last updated in NVD database

Technical Details for CVE-2026-48923

Vulnerability Analysis

The AppSpider Plugin exposes a form validation method that accepts a URL parameter from the requesting user. The method initiates an HTTP connection to the supplied URL to validate connectivity or configuration. The implementation does not enforce a permission check appropriate to the sensitivity of the action.

Form validation endpoints in Jenkins plugins are reachable through the standard descriptorByName URL pattern. Any authenticated user with Overall/Read permission can invoke them by issuing crafted HTTP requests to the controller. Because the request originates from the Jenkins controller process, it bypasses network boundaries that block external clients.

The outcome is a low-privilege server-side request forgery primitive. Attackers cannot read arbitrary response bodies in most cases, but they can probe internal hosts, ports, and HTTP services, and they can interact with metadata endpoints in cloud environments where the controller runs.

Root Cause

The root cause is missing authorization on a privileged action [CWE-269]. The form validation method should require Item/Configure or an equivalent permission before performing network operations on behalf of the caller. Instead, it inherits the default Overall/Read gate that protects most read-only Jenkins endpoints.

Attack Vector

An attacker first obtains valid credentials with Overall/Read permission. Many Jenkins instances grant this permission to all authenticated users or to anonymous users in misconfigured deployments. The attacker then submits an HTTP request to the vulnerable form validation endpoint, supplying a target URL such as an internal management interface, a cloud metadata service, or an attacker-controlled callback host. The Jenkins controller performs the request, and the attacker observes timing or error responses to infer information about the target.

The vulnerability is described in prose only because no public proof-of-concept code is referenced in the advisory. See the Jenkins Security Advisory 2026-05-27 for the authoritative description.

Detection Methods for CVE-2026-48923

Indicators of Compromise

Outbound HTTP or HTTPS requests from the Jenkins controller process to unexpected internal addresses, cloud metadata IPs such as 169.254.169.254, or unknown external hosts.
Access log entries showing requests to descriptorByName paths under the AppSpider Plugin namespace from low-privileged user accounts.
Repeated form validation calls from a single user session within short time intervals, indicating automated probing.

Detection Strategies

Review Jenkins access logs for requests matching the AppSpider Plugin descriptor URLs combined with user-supplied URL parameters.
Correlate Jenkins audit events with controller-side network telemetry to identify validation calls that produced outbound traffic to internal ranges.
Baseline the set of users who legitimately configure AppSpider scans, and alert when other accounts invoke the validation endpoint.

Monitoring Recommendations

Forward Jenkins controller HTTP access logs and process-level network telemetry to a centralized analytics platform for retention and correlation.
Alert on any connections from the Jenkins controller to RFC1918 ranges, link-local addresses, or cloud instance metadata endpoints that are not part of approved job activity.
Track installed plugin versions across all Jenkins controllers and flag instances still running AppSpider Plugin 1.0.17 or earlier.

How to Mitigate CVE-2026-48923

Immediate Actions Required

Inventory all Jenkins controllers and identify those with the AppSpider Plugin installed.
Restrict Overall/Read permission to trusted users, and disable anonymous read access until the plugin is updated or removed.
If the plugin is not in active use, uninstall it to eliminate the attack surface entirely.

Patch Information

At the time of publication, the Jenkins Security Advisory 2026-05-27 lists no fixed version for the AppSpider Plugin. Administrators should monitor the advisory page for an updated release and apply it as soon as it becomes available.

Workarounds

Remove or disable the AppSpider Plugin on controllers where it is not required.
Apply strict authorization strategies such as Role-Based Access Control to limit which users hold Overall/Read permission.
Place Jenkins controllers behind egress filtering that blocks connections to internal management networks and cloud metadata endpoints from the controller process.

bash

# Example: list AppSpider Plugin version via Jenkins CLI
java -jar jenkins-cli.jar -s https://jenkins.example.com/ \
  list-plugins | grep -i appspider

# Example: uninstall the plugin if not required
java -jar jenkins-cli.jar -s https://jenkins.example.com/ \
  disable-plugin appspider -restart