Privilege Escalation in Coder Remote Development Environments

Executive Summary

This vulnerability in the Coder platform involves a flaw in how workspace applications are managed across different tenants or workspaces. Specifically, the functions responsible for updating or inserting workspace apps do not properly verify that an app ID belongs to the workspace being built. This allows an attacker with elevated access (such as a template author or external provisioner operator) to rebind an existing app's agent ID to an agent they control, even if the app belongs to another workspace.

As a result, the attacker can redirect or proxy the victim's application traffic through their own agent, effectively hijacking the app's traffic across tenants. The vulnerability arises because the authorization layer does not block these cross-workspace upserts, and app UUIDs are discoverable via the public API.

The issue was fixed by adding checks to ensure that any existing workspace app row matches the workspace being built, rejecting any cross-workspace agent reassignment.

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Impact Analysis

If exploited, this vulnerability allows an attacker with elevated privileges to hijack application traffic from other tenants or workspaces by rebinding victim apps to attacker-controlled agents.

• The attacker can proxy or redirect IDE and terminal session traffic of the victim's application.
• This leads to a high confidentiality impact as sensitive data could be intercepted.
• There is also a high integrity impact because the attacker can manipulate or interfere with the victim's application traffic.

Exploitation requires elevated access, so only users with roles like template authors or external provisioner operators are at risk of abusing this vulnerability.

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Detection Guidance

Detection of this vulnerability involves identifying unauthorized cross-workspace agent rebindings where an app's agent_id is overwritten to redirect traffic to an attacker-controlled agent.

Since the vulnerability exploits the UpsertWorkspaceApp and insertAgentApp functions with a user-controlled app ID, monitoring logs for unexpected changes in workspace_apps entries or agent_id reassignments can help detect exploitation.

App UUIDs are discoverable through the public API, so commands that query workspace_apps for agent_id changes or cross-workspace bindings could be useful.

• Query the database for workspace_apps entries where the agent_id is assigned to a different workspace than the app's workspace.
• Monitor logs for calls to CompleteJob payloads that include app IDs not belonging to the workspace being built.
• Use SQL commands similar to: SELECT * FROM workspace_apps WHERE agent_workspace_id != app_workspace_id;
• Audit API usage for suspicious CompleteJob submissions with app IDs from other workspaces.

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Mitigation Strategies

The primary mitigation step is to upgrade Coder to a patched version that includes the fix for this vulnerability.

• Upgrade to one of the fixed versions: 2.29.17 or later, 2.32.7 or later, 2.33.8 or later, or 2.34.2 or later.

No known workarounds exist, so upgrading is essential to prevent exploitation.

Restrict elevated access to template authors and external provisioner operators to trusted personnel only, as exploitation requires such privileges.

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Compliance Impact

The vulnerability allows an attacker with elevated access to rebind a victim's application traffic to an attacker-controlled agent across different workspaces, potentially exposing sensitive data and compromising application integrity.

Such unauthorized access and data interception could lead to violations of data protection regulations like GDPR and HIPAA, which require strict controls on data confidentiality and integrity.

Because the vulnerability enables cross-tenant data proxying without proper authorization checks, organizations using affected versions of Coder may face compliance risks related to unauthorized data access and processing.

Mitigation requires upgrading to patched versions that enforce workspace ownership verification to prevent cross-workspace agent reassignment.

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