Summary
Coder's workspace agent API insecure redirect handling allowed cross-agent file read and write
Full technical description
agentConn.apiClient() used the default redirect behavior of http.Client while its custom transport dialed the host from the request URL as long as the port was the workspace agent HTTP API port (4). Agent tailnet IPs are deterministic from agent UUIDs, so a malicious workspace agent could return a redirect to another agent's tailnet IP and cause the control-plane client to send the follow-up workspace agent API request to the victim agent instead of the intended agent.
Redirects that preserve the method and body, such as HTTP 307 and 308, allow replay of write and process-start requests. HTTP 301, 302 and 303 redirects only convert POST requests to GET requests, so they are sufficient to demonstrate redirected reads but not write or command-execution primitives.
Workarounds
None. Upgrading is required.
Resources
- Fix: #26600
Impact
An authenticated user with a running workspace and control of a modified workspace agent can redirect workspace agent API requests made to their agent toward another online workspace agent reachable on the tailnet. If the attacker knows the victim agent UUID, they can derive the victim's tailnet IP and target the victim's file APIs to read or write files as the victim workspace user.
In affected versions that expose the workspace agent process API, the same primitive can be chained to command execution as the victim workspace user by writing a payload through the redirected file API and then redirecting a process-start request to execute it. This crosses workspace and tenant boundaries.
The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.
GHSA-QRWJ-VH9X-GW5V has a CVSS score of 8.3 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.34.4, 2.33.10, 2.32.9, 2.29.19); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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The fix disables automatic redirect following for workspace agent API clients and pins all workspace agent API dials to the intended agent's deterministic tailnet address. Requests whose URL host does not match the intended agent are rejected instead of being dialed.
The fix was backported to all supported release lines:
Frequently Asked Questions
- What is GHSA-QRWJ-VH9X-GW5V? GHSA-QRWJ-VH9X-GW5V is a high-severity incorrect authorization vulnerability in github.com/coder/coder/v2 (go), affecting versions >= 2.34.0, < 2.34.4. It is fixed in 2.34.4, 2.33.10, 2.32.9, 2.29.19. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
- How severe is GHSA-QRWJ-VH9X-GW5V? GHSA-QRWJ-VH9X-GW5V has a CVSS score of 8.3 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/coder/coder/v2 are affected by GHSA-QRWJ-VH9X-GW5V? github.com/coder/coder/v2 (go) versions >= 2.34.0, < 2.34.4 is affected.
- Is there a fix for GHSA-QRWJ-VH9X-GW5V? Yes. GHSA-QRWJ-VH9X-GW5V is fixed in 2.34.4, 2.33.10, 2.32.9, 2.29.19. Upgrade to this version or later.
- Is GHSA-QRWJ-VH9X-GW5V exploitable, and should I be worried? Whether GHSA-QRWJ-VH9X-GW5V is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-QRWJ-VH9X-GW5V is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-QRWJ-VH9X-GW5V?
- Upgrade
github.com/coder/coder/v2to 2.34.4 or later - Upgrade
github.com/coder/coder/v2to 2.33.10 or later - Upgrade
github.com/coder/coder/v2to 2.32.9 or later - Upgrade
github.com/coder/coder/v2to 2.29.19 or later
- Upgrade