Executive Summary

This vulnerability is an information leak in certain versions of React Server Components (19.0.0 through 19.2.1) and related packages. It occurs when a specially crafted HTTP request is sent to a vulnerable Server Function, which may then unsafely return the source code of any Server Function. Exploitation requires that the Server Function exposes a stringified argument either explicitly or implicitly.

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Compliance Impact

The provided resources do not specify how this vulnerability affects compliance with common standards and regulations such as GDPR or HIPAA.

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Detection Guidance

Detection involves monitoring for crafted malicious HTTP requests targeting Server Function endpoints that may return source code unexpectedly. Specific commands are not provided in the available resources. However, inspecting HTTP request logs for unusual requests to Server Functions and verifying if any Server Function exposes stringified arguments can help identify potential exploitation attempts. [1]

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Mitigation Strategies

The immediate mitigation step is to upgrade React Server Components packages to fixed versions 19.0.2, 19.1.3, or 19.2.2. Users who updated for the prior critical vulnerability (CVE-2025-55182) must update again, as earlier patches remain vulnerable. Avoid using vulnerable versions 19.0.0 through 19.2.1. Additionally, monorepo users should update only the impacted packages to prevent version mismatches. Temporary mitigations coordinated with hosting providers exist, but upgrading packages is strongly recommended. [1]

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Detection Guidance

Detection involves monitoring for crafted malicious HTTP requests sent to Server Function endpoints that may cause source code exposure. Specific detection commands are not provided in the resources. However, inspecting HTTP request logs for unusual or suspicious requests targeting Server Functions, especially those including stringified arguments, may help identify exploitation attempts. [1]

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Mitigation Strategies

The immediate mitigation step is to upgrade React Server Components packages to fixed versions 19.0.2, 19.1.3, or 19.2.2. Users who updated for the prior critical vulnerability (CVE-2025-55182) must update again, as earlier patches remain vulnerable. The fix prevents stringification of Server Function source code, mitigating the exposure risk. Additionally, React Native users not using monorepos or react-dom are unaffected, but monorepo users should update only the impacted packages to avoid version mismatches. [1]

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Impact Analysis

The vulnerability can lead to unauthorized disclosure of source code of Server Functions, potentially exposing sensitive implementation details. This information leak could aid attackers in understanding the server-side logic, which might be leveraged for further attacks or exploitation.

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