Eclipse Theia CVE-2026-19884

Exploitation requires the victim to be running Eclipse Theia version 1.69.0 or earlier, or a Theia-based downstream application that includes the @theia/git extension or the bundled VS Code git extension - both are present by default in standard Theia distributions. The victim must open a folder that contains an attacker-controlled .git/config specifying core.fsmonitor or a functionally equivalent hook-like git configuration setting. The malicious repository can be delivered through a standard git clone operation using the OVE-20210718-0001 technique, which embeds a bare repository inside a regular repository so the malicious configuration is not immediately visible to the cloning user. No authentication, elevated privileges, or non-default Theia configuration is required. Exploitation is bounded by the requirement for active user interaction: the victim must explicitly open the folder or repository in the IDE (CVSS UI:A). Eclipse Theia 1.70.0 and later are not exploitable because untrusted workspace enforcement blocks git plugins from executing before the workspace is granted trust.

The CVSS 4.0 score of 8.4 (High) reflects a local attack vector requiring active user interaction (UI:A) with no privileges needed (PR:N) and high impact across confidentiality, integrity, and availability on the vulnerable system. The UI:A requirement is a meaningful constraint: automated, opportunistic exploitation at scale is not feasible - the attacker must induce the victim to clone and open a repository in Theia. EPSS data was not included in the intelligence package, so exploitation probability cannot be quantitatively anchored, and no CISA KEV listing was identified, which suggests this has not been observed in widespread active exploitation campaigns. No proof-of-concept exploit targeting Theia specifically was confirmed, though the underlying git hook abuse technique (OVE-20210718-0001) is publicly documented and well understood by offensive practitioners, meaning the attack is readily constructable. The absence of a scope change (SC:N/SI:N/SA:N) confirms blast radius is confined to the victim's own user session. Given that developer workflows routinely involve cloning and exploring external repositories, even a mid-sized municipal IT team in opole maintaining a Theia-based cloud IDE for their developers should treat this as an urgent patch priority, since user behavior naturally aligns with the attack preconditions. The risk is highest for organizations deploying shared Theia-based IDE environments where developers regularly open third-party or community-contributed repositories.

An attacker publishes a git repository that contains a nested bare repository with a .git/config file setting core.fsmonitor to a malicious shell command, exploiting the OVE-20210718-0001 delivery technique. A developer clones the repository to evaluate its contents and opens the resulting folder in a Theia-based IDE running version 1.69.0 or earlier; with no trust prompt displayed, the git extension immediately runs git status, which reads the attacker-controlled .git/config and executes the configured command with the developer's user privileges.