GHSA-h856-ffvv-xvr4
CRITICALJenkins Remoting library arbitrary file read vulnerability
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
org.jenkins-ci.main:remoting☕org.jenkins-ci.main:remoting☕org.jenkins-ci.main:remoting☕org.jenkins-ci.main:jenkins-core☕org.jenkins-ci.main:jenkins-core☕org.jenkins-ci.main:jenkins-coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Jenkins uses the Remoting library (typically agent.jar or remoting.jar) for the communication between controller and agents. This library allows agents to load classes and classloader resources from the controller, so that Java objects sent from the controller (build steps, etc.) can be executed on agents.
In addition to individual class and resource files, Remoting also allows Jenkins plugins to transmit entire jar files to agents using the Channel#preloadJar API. As of publication of this advisory, this feature is used by the following plugins distributed by the Jenkins project: bouncycastle API, Groovy, Ivy, TeamConcert
In Remoting 3256.v88a_f6e922152 and earlier, except 3206.3208.v409508a_675ff and 3248.3250.v3277a_8e88c9b_, included in Jenkins 2.470 and earlier, LTS 2.452.3 and earlier, calls to Channel#preloadJar result in the retrieval of files from the controller by the agent using ClassLoaderProxy#fetchJar. Additionally, the implementation of ClassLoaderProxy#fetchJar invoked on the controller does not restrict paths that agents could request to read from the controller file system.
This allows agent processes, code running on agents, and attackers with Agent/Connect permission to read arbitrary files from the Jenkins controller file system.
The Remoting library in Jenkins 2.471, LTS 2.452.4, LTS 2.462.1 now sends jar file contents with Channel#preloadJar requests, the only use case of ClassLoaderProxy#fetchJar in agents, so that agents do not need to request jar file contents from controllers anymore.
To retain compatibility with older versions of Remoting in combination with the plugins listed above, ClassLoaderProxy#fetchJar is retained and otherwise unused, just deprecated. Its implementation in Jenkins 2.471, LTS 2.452.4, LTS 2.462.1 was changed so that it is now limited to retrieving jar files referenced in the core classloader or any plugin classloader.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.jenkins-ci.main:remoting | all versions | 3206.3208 |
| ☕Maven | org.jenkins-ci.main:remoting | ≥ 3248&&< 3248.3250 | 3248.3250 |
| ☕Maven | org.jenkins-ci.main:remoting | ≥ 3256&&< 3256.3258 | 3256.3258 |
| ☕Maven | org.jenkins-ci.main:jenkins-core | all versions | 2.452.4 |
| ☕Maven | org.jenkins-ci.main:jenkins-core | ≥ 2.460&&< 2.462.1 | 2.462.1 |
| ☕Maven | org.jenkins-ci.main:jenkins-core | ≥ 2.470&&< 2.471 | 2.471 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.jenkins-ci.main:remoting. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.jenkins-ci.main:remoting to 3206.3208 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-h856-ffvv-xvr4 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-h856-ffvv-xvr4 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-h856-ffvv-xvr4. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-h856-ffvv-xvr4 in your dependencies?
O3 detects GHSA-h856-ffvv-xvr4 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.