CVE-2026-118687: Coder missing audience validation in GCP instance-identity endpoint

CVE-2026-118687 · Severity: medium · CVSS 6.5 · Published 2026-10-28

Coder is a remote development platform that provisions workspaces on cloud infrastructure including Google Compute Engine. The authentication endpoint for workspace agents fails to validate the intended recipient of GCP identity tokens, allowing an attacker who obtains a token from one service to replay it against Coder and hijack a workspace agent's session. This could grant unauthorized access to a developer's workspace until the next build.

Technologies: Coder. Vendors: Coder.

Quick answers

Is CVE-2026-118687 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-118687 being exploited in the wild.
How severe is CVE-2026-118687?
Medium severity, with a CVSS score of 6.5, published 28 October 2026.
Which products and versions are affected?
Coder before 2.29.21, 2.30.0 before 2.34.12, 2.35.0 before 2.35.9, 2.36.0 before 2.36.7, 2.37.0 before 2.37.4.
Is there a fix for CVE-2026-118687?
Yes: fixed in 2.29.21, 2.34.12, 2.35.9, 2.36.7, 2.37.4. Until then: Affected deployments using GCP instance identity for agents may switch templates to token authentication (auth = "token") and restart workspaces to issue new agent tokens. Do not log or forward GCE identity tokens from workspace VMs, and use format=standard tokens for third-party services instead of format=full.</anigation> <parameter name="timeline">[{"kind": "advisory", "at": "2026-10-13"}, {"kind": "disclosed", "at": "2026-10-28"}] Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-118687 attacked?
It is attacked over the network.
Am I affected by CVE-2026-118687?
Check whether you run Coder at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • Fixed in: 2.29.21, 2.34.12, 2.35.9, 2.36.7, 2.37.4

Affected deployments using GCP instance identity for agents may switch templates to token authentication (auth = "token") and restart workspaces to issue new agent tokens. Do not log or forward GCE identity tokens from workspace VMs, and use format=standard tokens for third-party services instead of format=full.</anigation> <parameter name="timeline">[{"kind": "advisory", "at": "2026-10-13"}, {"kind": "disclosed", "at": "2026-10-28"}]

Technical details

The POST /api/v2/workspaceagents/google-instance-identity endpoint verifies the Google signature and expiry of instance-identity JWTs but does not validate the audience (aud) claim, allowing token replay from other relying parties (CWE-441 confused deputy). An attacker with an unexpired format=full GCP identity token minted for another service can exchange it for that workspace agent's session token, which persists until the workspace's next build—far longer than the ~1 hour token lifetime. The fix enforces the aud claim to equal "coder".

Affected products

  • Coder Coder before 2.29.21, 2.30.0 before 2.34.12, 2.35.0 before 2.35.9, 2.36.0 before 2.36.7, 2.37.0 before 2.37.4

References

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