Coder: Missing audience validation in GCP instance-identity authentication
Summary
Coder does not check the audience (aud) claim of Google Compute Engine instance-identity tokens at the workspace agent authentication endpoint POST /api/v2/workspaceagents/google-instance-identity. An attacker who obtains an unexpired format=full identity token issued for another relying party can replay it to obtain the session token of that workspace agent. This session token remains valid until the workspace's next build. Only deployments that use GCP instance-identity authentication for workspace agents on Google Compute Engine are affected.
Affected
- Coder 2.37.0 to before 2.37.4
- Coder 2.36.0 to before 2.36.7
- Coder 2.35.0 to before 2.35.9
- Coder 2.30.0 to before 2.34.12
- Coder before 2.29.21
Fixed in
- 2.37.4
- 2.36.7
- 2.35.9
- 2.34.12
- 2.29.21
- Fixed in 2.38.0 and backported to the listed branches
Workaround
- Switch affected templates to token authentication (auth = "token") and restart the workspaces so that new agent tokens are issued.
- Do not log or forward GCE identity tokens from workspace VMs. Use format=standard tokens for third-party services, because they cannot be exchanged at this endpoint.
Exploitation
- No public exploit known according to VulDB.
- Not known to be exploited in the wild.
- CISA SSVC: exploitation none, automatable no, technical impact partial.
- EPSS: 0.19 %.
Our recommendation
- Check whether any Coder instance uses GCP instance-identity authentication for workspace agents.
- Upgrade to the fixed version of your branch (2.29.21, 2.34.12, 2.35.9, 2.36.7, 2.37.4 or later; 2.38.0 or later is the upstream fix).
- Rebuild affected workspaces after the upgrade so that existing agent sessions expire.
- Check custom agent clients, because requests with another audience are rejected with HTTP 401 and must request audience=coder.
- Review logs for unusual requests to /api/v2/workspaceagents/google-instance-identity.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- GitHub Security Advisory GHSA-24vh-q7rg-243w github.com
- VulnCheck advisory www.vulncheck.com
- Coder pull request #29765 (fix) github.com
- Coder pull request #30195 github.com
- VulDB CVE-2026-118687 vuldb.com
- Vulners CVE-2026-118687 vulners.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 13:06.
Original description (NVD)
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, and 2.37.0 before 2.37.4 does not validate the audience claim of GCE instance-identity JWTs at the POST /api/v2/workspaceagents/google-instance-identity endpoint. Attackers who obtain an unexpired format=full identity token minted for another relying party can replay it to obtain that workspace agent's session token, which remains valid until the workspace's next build.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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