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EUVD-2026-333854

fkie_cve-2026-46354

Coder allows organizations to provision remote development environments via Terraform. In versions prior tp 2.24.5, 2.29.13, 2.30.8, 2.31.12, 2.32.2, and 2.33.3, `azureidentity.Validate()` verifies that the PKCS#7 signer certificate chains to a trusted Azure CA but never verifies the PKCS#7 signature itself. An attacker can embed a legitimate Azure certificate alongside arbitrary content e.g. `{"vmId":"<target>"}` and the forged `vmId` will be accepted returning the victim workspace agent's session token. No authentication is required. The attacker only needs to know a target VM's `vmId` which is a `UUIDv4`. That's a practical limitation which would typically require prior access to be exploited. Versions 2.24.5, 2.29.13, 2.30.8, 2.31.12, 2.32.2, and 2.33.3 patch the issue. As a workaround, reconfigure any Azure templates to use token authentication rather than `azure-instance-identity`.

GHSA-6x44-w3xg-hqqf — Coder: PKCS#7 signature bypass in Azure instance identity allows unauthenticated agent token theft

Affected: Go: github.com/coder/coder/v2, Go: github.com/coder/coder

## Summary

`azureidentity.Validate()` verifies that the PKCS#7 signer certificate chains to a trusted Azure CA but never verifies the PKCS#7 signature itself. An attacker can embed a legitimate Azure certificate alongside arbitrary content e.g. `{"vmId":"<target>"}` and the forged `vmId` will be accepted returning the victim workspace agent's session token.

**No authentication is required.** The attacker only needs to know a target VM's `vmId` which is a `UUIDv4`. > that's a practical limitation which would typically require prior access to be exploited

## Root Cause

In unpatched Coder releases the signature over the PKCS#7 content is not validated - only the signing certificate is checked.

## Impact

An attacker on any Azure VM or with access to a publicly available Azure IMDS certificate from CT logs can:

1. **Steal an agent session token** by sending a forged PKCS#7 envelope to `POST /api/v2/workspaceagents/azure-instance-identity` which is unauthenticated. 2. **With the stolen token** access: - **Git SSH private key** via `GET /workspaceagents/me/gitsshkey`: push to repositories and impersonate the workspace owner. - **OAuth access tokens** via `GET /workspaceagents/me/external-auth`: GitHub, GitLab, and Bitbucket tokens in plaintext. - **Workspace secrets** via the agent manifest: environment variables, file paths, and API keys.

## Attack Path Diagram

<img width="5588" height="4176" alt="PKCS7_diagram (1)" src="https://github.com/user-attachments/assets…