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Post-authentication Groovy sandbox bypass RCE in Apache Syncope
CVE-2026-42782 is an improper isolation or compartmentalization vulnerability in Apache Syncope that affects the handling of Groovy-based implementations. An administrator with sufficient entitlements to manage Implementations can create a malicious Groovy class containing untrusted code that reaches a non-sandboxed execution path through the class static initializer. Because the static initializer was not forced to execute within the intended sandbox, attacker-supplied Groovy code could escape the expected execution restrictions and run within the Syncope application context. Affected versions are Apache Syncope 3.0 through 3.0.16, 4.0 through 4.0.5, and 4.1.0.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation results in post-authentication remote code execution within the Apache Syncope server context. An attacker who already holds administrative privileges and the required Implementations entitlements can execute arbitrary untrusted Groovy code outside the intended sandbox boundaries, potentially compromising the confidentiality, integrity, and availability of the Syncope instance and any resources reachable from it.
If you can’t patch tonight, do this now.
Restrict administrative access and specifically limit the Implementations entitlement to only highly trusted administrators. Review and reduce roles capable of creating or modifying Groovy implementations, and avoid allowing untrusted or unnecessary custom Groovy code in Syncope until patched versions are deployed. Where immediate upgrade is not possible, closely monitor administrative changes involving implementations and custom scripting features.
Patch, then assume compromise.
Upgrade Apache Syncope to version 4.0.6 or 4.1.1, which fix the issue by forcing Groovy static initializers to execute inside the sandbox. Systems running affected 3.0.x releases should be moved to a fixed supported release because 3.0 through 3.0.16 are affected.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
3 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.