CVE-2026-70426 in Jenkins
Summary
by MITRE • 08/05/2026
In Remoting 3384.v60d89463d9e0 and earlier, except 3355.3357.v931d3c992987, included in Jenkins 2.575 and earlier, LTS 2.568.1 and earlier, the JEP-200 class filter is not applied to classes resolved via a fallback path in the Remoting deserialization implementation, allowing agent processes, code running on agents, and attackers with Agent/Connect permission to bypass the JEP-200 deserialization filter for classes on the Jenkins core classpath.
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Analysis
by VulDB Data Team • 08/05/2026
This vulnerability exists within the Remoting component of Jenkins versions 3384.v60d89463d9e0 and earlier, excluding version 3355.3357.v931d3c992987, affecting Jenkins 2.575 and earlier releases as well as LTS 2.568.1 and earlier versions. The flaw resides in the deserialization implementation where the JEP-200 class filter mechanism fails to properly protect against unauthorized class loading through a fallback path mechanism. This represents a critical security oversight that undermines the fundamental security controls designed to prevent deserialization of potentially malicious classes.
The technical implementation issue stems from how Jenkins handles class resolution during deserialization operations. When objects are being deserialized, the system should enforce strict filtering based on JEP-200 rules that restrict which classes can be loaded from the core classpath. However, the fallback path mechanism bypasses these security controls, allowing unauthorized code execution through legitimate class paths that should otherwise be restricted. This creates a pathway where attacker-controlled data can trigger deserialization of classes that would normally be blocked by the security filter.
The operational impact of this vulnerability is severe as it enables privilege escalation and arbitrary code execution on Jenkins agents. An attacker with Agent/Connect permission can leverage this flaw to bypass security restrictions that should prevent loading of dangerous classes from Jenkins core. This effectively means that malicious actors can execute arbitrary code on agent nodes, potentially leading to complete system compromise. The vulnerability affects not just the agent processes themselves but also code running within those processes, creating a wide attack surface for exploitation.
This issue aligns with CWE-502 which describes deserialization of untrusted data, and maps to ATT&CK technique T1059.007 for command and scripting interpreter. The vulnerability demonstrates how insufficient input validation in deserialization pathways can be exploited to bypass security controls that are fundamental to preventing code injection attacks. Organizations should immediately upgrade to patched versions of Jenkins and Remoting components to address this critical flaw.
The remediation approach requires immediate patching of Jenkins installations to versions that contain the fixed JEP-200 class filter implementation. Administrators should also review and tighten permissions for agent connections, as the vulnerability specifically requires Agent/Connect permission to exploit. Additionally, organizations should consider implementing network segmentation and monitoring for unusual deserialization activities that might indicate exploitation attempts, since this vulnerability represents a sophisticated attack vector that can bypass traditional security controls.