HighPublic exploit

Unauthorized WebSocket Access in Claude Code IDE Extensions

IdentifiersCVE-2025-52882CWE-306

CVE-2025-52882 affects Anthropic Claude Code extensions/plugins for VSCode and forks (including Cursor, Windsurf, and VSCodium) and JetBrains IDEs (including IntelliJ, PyCharm, and Android Studio). Vulnerable versions exposed a local WebSocket interface that could be reached by attacker-controlled webpages without authentication. In VSCode-based environments, affected versions are 0.2.116 through 1.0.23; in JetBrains IDEs, affected Claude Code [beta] plugin versions are 0.1.1 through 0.1.8. Because browsers permit WebSocket connections to localhost outside normal same-origin protections, a malicious site could connect to the local Claude Code service and interact with IDE-exposed functionality. Reported consequences in VSCode include arbitrary file read, enumeration of files open in the IDE, access to selection and diagnostics events, and limited code execution scenarios when the user has an open Jupyter Notebook and accepts a malicious prompt. In JetBrains IDEs, the exposed data includes selection events, open-file lists, and syntax-error information. The patch added authentication for WebSocket connections and was released by Claude on June 13, 2025.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows a remote attacker, via a malicious webpage visited by the victim, to access data and IDE context from the local development environment. In VSCode-based IDEs, this can include reading arbitrary local files, enumerating open files, and receiving editor selection and diagnostics events, creating significant confidentiality exposure for source code, secrets, and project metadata. In limited cases involving an open Jupyter Notebook and user acceptance of a malicious prompt, the issue can also lead to code execution. In JetBrains IDEs, the impact is more limited but still exposes sensitive development context such as open files, selection events, and syntax errors. Overall, the vulnerability enables cross-origin access from the web into a local privileged developer tool context.

Mitigation

If you can’t patch tonight, do this now.

Until patched, reduce exposure by disabling or uninstalling the Claude Code extension/plugin, avoiding visits to untrusted or attacker-controlled websites while the IDE is running, and closing the IDE when not in use. Organizations can also restrict browser access patterns to localhost services where feasible, monitor for unexpected localhost WebSocket activity, and limit use of Jupyter notebooks in affected environments. However, the primary mitigation is to upgrade to the fixed versions because the root issue is missing authentication on the local WebSocket interface.

Remediation

Patch, then assume compromise.

Update Claude Code for VSCode and all VSCode forks to version 1.0.24 or later. Update Claude Code [Beta] for JetBrains IDEs to version 0.1.9 or later. If updating is not possible, uninstall vulnerable versions. After updating or uninstalling, restart the IDE to ensure the patched extension/plugin is loaded and any vulnerable local service is no longer running. Anthropic also removed vulnerable versions from extension stores and introduced authentication tokens for WebSocket connections.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

6 SOURCESView more in app

the hacker newsNews

Oct 27, 2025

⚡ Weekly Recap: WSUS Exploited, LockBit 5.0 Returns, Telegram Backdoor, F5 Breach Widens

A vulnerability listed as trending; no technical details provided in the content.

datadog security labsNews

Aug 26, 2025

CVE-2025-52882: WebSocket authentication bypass in Claude Code extensions

A critical vulnerability in Anthropic's Claude Code extensions for VS Code and other IDEs that allowed unauthenticated local WebSocket connections, enabling remote command execution and file read via browser-based attacks. The flaw was due to a lack of authentication on the local WebSocket server used by the extension.

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Exposure mapping

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Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

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Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity4