CVE-2026-46354: Coder PKCS#7 Signature Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6x44-w3xg-hqqf",
  "modified" : "2026-05-19T20:04:13Z",
  "published" : "2026-05-19T20:04:13Z",
  "aliases" : [ "CVE-2026-46354" ],
  "summary" : "Coder: PKCS#7 signature bypass in Azure instance identity allows unauthenticated agent token theft",
  "details" : "## Summary\n\n`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.\n\n**No authentication is required.** The attacker only needs to know a target VM's `vmId` which is a `UUIDv4`.\n> that's a practical limitation which would typically require prior access to be exploited\n\n## Root Cause\n\nIn unpatched Coder releases the signature over the PKCS#7 content is not validated - only the signing certificate is checked.\n\n## Impact\n\nAn attacker on any Azure VM or with access to a publicly available Azure IMDS certificate from CT logs can:\n\n1. **Steal an agent session token** by sending a forged PKCS#7 envelope to `POST /api/v2/workspaceagents/azure-instance-identity` which is unauthenticated.\n2. **With the stolen token** access:\n   - **Git SSH private key** via `GET /workspaceagents/me/gitsshkey`: push to repositories and impersonate the workspace owner.\n   - **OAuth access tokens** via `GET /workspaceagents/me/external-auth`: GitHub, GitLab, and Bitbucket tokens in plaintext.\n   - **Workspace secrets** via the agent manifest: environment variables, file paths, and API keys.\n\n## Attack Path Diagram\n\n<img width=\"5588\" height=\"4176\" alt=\"PKCS7_diagram (1)\" src=\"https://github.com/user-attachments/assets/74e88a89-a995-450d-87ab-6feed03579a5\" />\n\n## Affected Versions\n\nAll versions of Coder v2 are affected.\n\n## Patches\n\nFixed in [#25286 ](https://github.com/coder/coder/pull/25286)\n\nThe fix was backported to all supported release lines:\n\n| Patched Versions |\n| --- |\n| [**v2.33.3**](https://github.com/coder/coder/releases/tag/v2.33.3) |\n| [**v2.32.2**](https://github.com/coder/coder/releases/tag/v2.32.2) |\n| [**v2.31.12**](https://github.com/coder/coder/releases/tag/v2.31.12) |\n| [**v2.30.8**](https://github.com/coder/coder/releases/tag/v2.30.8) |\n| [**v2.29.13**](https://github.com/coder/coder/releases/tag/v2.29.13) |\n| [**v2.24.5**](https://github.com/coder/coder/releases/tag/v2.24.5) |\n\n## Workarounds\n\nIf unable to patch we recommend immediately reconfiguring any Azure templates to use token authentication rather than `azure-instance-identity` until the patch is released and you are fully upgraded.\n\n1. Modify the [`coder_agent.auth`](https://registry.terraform.io/providers/coder/coder/latest/docs/resources/agent#auth-1) value to be `token`.\n2. Add `CODER_AGENT_TOKEN=${coder_agent.main.token}` to the set of environment variables for the Coder Workspace Agent initialization script.\n\n## Recognition\n\nWe'd like to thank [Ben Tran](https://github.com/bencalif) of [calif.io](http://calif.io) and Anthropic’s Security Team (`ANT-2026-22445`) for independently disclosing this issue!",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/coder/coder/v2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.33.0-rc.0"
      }, {
        "fixed" : "2.33.3"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/coder/coder/v2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.32.0-rc.0"
      }, {
        "fixed" : "2.32.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/coder/coder/v2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.31.0"
      }, {
        "fixed" : "2.31.12"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/coder/coder/v2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.30.0"
      }, {
        "fixed" : "2.30.8"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/coder/coder/v2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.29.0"
      }, {
        "fixed" : "2.29.13"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/coder/coder/v2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.24.5"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/coder/coder"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "0.27.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/coder/coder/security/advisories/GHSA-6x44-w3xg-hqqf"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/coder/coder/pull/25286"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/coder/coder"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/coder/coder/releases/tag/v2.24.5"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/coder/coder/releases/tag/v2.29.13"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/coder/coder/releases/tag/v2.30.8"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/coder/coder/releases/tag/v2.31.12"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/coder/coder/releases/tag/v2.32.2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/coder/coder/releases/tag/v2.33.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-347" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-19T20:04:13Z",
    "nvd_published_at" : null
  }
}