What is CVE-2026-55429?

CVE-2026-55429 is a high-severity security vulnerability in github.com/coder/coder/v2 (go), affecting versions >= 2.34.0, < 2.34.2. It is fixed in 2.34.2, 2.33.8, 2.32.7, 2.29.17.

How severe is CVE-2026-55429?

CVE-2026-55429 has a CVSS score of 8.7 (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 CVE-2026-55429?

github.com/coder/coder/v2 (go) versions >= 2.34.0, < 2.34.2 is affected.

Is there a fix for CVE-2026-55429?

Yes. CVE-2026-55429 is fixed in 2.34.2, 2.33.8, 2.32.7, 2.29.17. Upgrade to this version or later.

Is CVE-2026-55429 exploitable, and should I be worried?

Whether CVE-2026-55429 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.

What actually determines whether CVE-2026-55429 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 CVE-2026-55429?

Upgrade: github.com/coder/coder/v2 to 2.34.2 or later, github.com/coder/coder/v2 to 2.33.8 or later, github.com/coder/coder/v2 to 2.32.7 or later, github.com/coder/coder/v2 to 2.29.17 or later.

CVE-2026-55429 in github.com/coder/coder/v2

Q: How severe is CVE-2026-55429?

CVE-2026-55429 has a CVSS score of 8.7 (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.

Q: Which versions of github.com/coder/coder/v2 are affected by CVE-2026-55429?

github.com/coder/coder/v2 (go) versions >= 2.34.0, < 2.34.2 is affected.

Q: Is there a fix for CVE-2026-55429?

Yes. CVE-2026-55429 is fixed in 2.34.2, 2.33.8, 2.32.7, 2.29.17. Upgrade to this version or later.

Q: Is CVE-2026-55429 exploitable, and should I be worried?

Whether CVE-2026-55429 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.

Q: What actually determines whether CVE-2026-55429 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.

Q: How do I fix CVE-2026-55429?

Upgrade: github.com/coder/coder/v2 to 2.34.2 or later, github.com/coder/coder/v2 to 2.33.8 or later, github.com/coder/coder/v2 to 2.32.7 or later, github.com/coder/coder/v2 to 2.29.17 or later.

Summary

Coder's workspace app upsert allows cross-workspace agent rebinding via user-controlled app ID

Full technical description

UpsertWorkspaceApp overwrites an existing app's agent_id on a primary-key conflict and insertAgentApp accepts the app ID from the provisioner's CompleteJob payload without verifying it belongs to the workspace being built. CompleteJob runs under dbauthz.AsProvisionerd so the authorization layer does not block the cross-workspace upsert.

Note: Exploitation requires elevated access as a template author or external provisioner operator.

Workarounds

None. Upgrading is required.

Resources

Fix: #26103

Credits

Coder would like to thank Anthropic's Security Team (ANT-2026-22441) for independently disclosing this issue!

Impact

A user with template authorship or external provisioner access can submit a CompleteJob payload with a known victim app UUID and an attacker-controlled agent ID. On completion of the attacker's build the victim's app row is rebound to the attacker's agent so later app traffic such as IDE and terminal sessions is proxied to the attacker's workspace. App UUIDs are discoverable through the public API.

CVE-2026-55429 has a CVSS score of 8.7 (High). The vector is network-reachable, high 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 (2.34.2, 2.33.8, 2.32.7, 2.29.17); upgrading removes the vulnerable code path.

Affected versions

github.com/coder/coder/v2 (>= 2.34.0, < 2.34.2) github.com/coder/coder/v2 (>= 2.33.0, < 2.33.8) github.com/coder/coder/v2 (>= 2.30.0, < 2.32.7) github.com/coder/coder/v2 (< 2.29.17)

Security releases

github.com/coder/coder/v2 → 2.34.2 (go) github.com/coder/coder/v2 → 2.33.8 (go) github.com/coder/coder/v2 → 2.32.7 (go) github.com/coder/coder/v2 → 2.29.17 (go)

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.

Already deployed Kodem?

See it in your environment New to Kodem? Get a demo →

Remediation advice

The fix verifies that any existing workspace_apps row matching the supplied ID belongs to the workspace being built and rejects cross-workspace agent reassignment.

The fix was backported to all supported release lines:

Release line	Patched version
2.34	v2.34.2
2.33	v2.33.8
2.32	v2.32.7
2.29 (ESR)	v2.29.17

Frequently Asked Questions

What is CVE-2026-55429? CVE-2026-55429 is a high-severity security vulnerability in github.com/coder/coder/v2 (go), affecting versions >= 2.34.0, < 2.34.2. It is fixed in 2.34.2, 2.33.8, 2.32.7, 2.29.17.
How severe is CVE-2026-55429? CVE-2026-55429 has a CVSS score of 8.7 (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 CVE-2026-55429? github.com/coder/coder/v2 (go) versions >= 2.34.0, < 2.34.2 is affected.
Is there a fix for CVE-2026-55429? Yes. CVE-2026-55429 is fixed in 2.34.2, 2.33.8, 2.32.7, 2.29.17. Upgrade to this version or later.
Is CVE-2026-55429 exploitable, and should I be worried? Whether CVE-2026-55429 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 CVE-2026-55429 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 CVE-2026-55429?
- Upgrade github.com/coder/coder/v2 to 2.34.2 or later
- Upgrade github.com/coder/coder/v2 to 2.33.8 or later
- Upgrade github.com/coder/coder/v2 to 2.32.7 or later
- Upgrade github.com/coder/coder/v2 to 2.29.17 or later

Other vulnerabilities in github.com/coder/coder/v2

CVE-IDSeverityPackage summary

GHSA-QRWJ-VH9X-GW5VHighgithub.com/coder/coder/v2: Coder's workspace agent API insecure redirect handling allowed cross-agent file read and write CVE-2026-55438Mediumgithub.com/coder/coder/v2: Coder's workspace app CORS origin check can be bypassed via UUID-based subdomain spoofing CVE-2026-55437Mediumgithub.com/coder/coder/v2: Coder vulnerable to stored HTML injection via workspace agent logs in AgentLogLine component CVE-2026-55436Highgithub.com/coder/coder/v2: Coder's AI Bridge Proxy skips TLS certificate verification in default configuration CVE-2026-55435Mediumgithub.com/coder/coder/v2: Suspended Coder users retain access to AI Bridge LLM proxy endpoints