GHSA-9R87-MVCW-X35F

Vulnerability from github – Published: 2026-07-06 20:52 – Updated: 2026-07-06 20:52
VLAI
Summary
Coder vulnerable to OIDC account takeover via email-based user matching and email_verified bypass
Details

Summary

Two flaws in Coder's OIDC login chained into account takeover: email-based user matching fell back to linking by email without checking for an existing link to a different IdP subject and the email_verified claim was only enforced when present as a boolean false so an absent or non-boolean claim was treated as verified.

Impact

An attacker who could authenticate at the configured OIDC provider with an email matching a victim's Coder account could log in as that victim and gain full access to their workspaces, templates and resources. This required OIDC authentication, attacker control of a matching email at the IdP and a victim account not yet linked to a different IdP subject.

Patches

The fix restricts the email fallback to first-time and legacy linking and defaults email_verified to false when the claim is absent or of an unexpected type.

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

Workarounds

Configure the OIDC provider to disallow self-registration or to require email verification before issuing tokens.

Resources

  • Fix: #25712, #25713

Credits

Coder would like to thank Anthropic's Security Team (ANT-2026-22450) for independently disclosing this issue!

Severity
7.4 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Show details on source website
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/coder/coder/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.34.0"
            },
            {
              "fixed": "2.34.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/coder/coder/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.33.0"
            },
            {
              "fixed": "2.33.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/coder/coder/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.30.0"
            },
            {
              "fixed": "2.32.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/coder/coder/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.29.17"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55075"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-287",
      "CWE-289"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-06T20:52:13Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\n\nTwo flaws in Coder\u0027s OIDC login chained into account takeover: email-based user matching fell back to linking by email without checking for an existing link to a different IdP subject and the `email_verified` claim was only enforced when present as a boolean `false` so an absent or non-boolean claim was treated as verified.\n\n### Impact\n\nAn attacker who could authenticate at the configured OIDC provider with an email matching a victim\u0027s Coder account could log in as that victim and gain full access to their workspaces, templates and resources. This required OIDC authentication, attacker control of a matching email at the IdP and a victim account not yet linked to a different IdP subject.\n\n### Patches\n\nThe fix restricts the email fallback to first-time and legacy linking and defaults `email_verified` to false when the claim is absent or of an unexpected type.\n\nThe fix was backported to all supported release lines:\n\n| Release line | Patched version |\n|---|---|\n| 2.34 | [v2.34.2](https://github.com/coder/coder/releases/tag/v2.34.2) |\n| 2.33 | [v2.33.8](https://github.com/coder/coder/releases/tag/v2.33.8) |\n| 2.32 | [v2.32.7](https://github.com/coder/coder/releases/tag/v2.32.7) |\n| 2.29 (ESR) | [v2.29.17](https://github.com/coder/coder/releases/tag/v2.29.17) |\n\n### Workarounds\n\nConfigure the OIDC provider to disallow self-registration or to require email verification before issuing tokens.\n\n### Resources\n\n- Fix: #25712, #25713\n\n### Credits\n\nCoder would like to thank Anthropic\u0027s Security Team (ANT-2026-22450) for independently disclosing this issue!",
  "id": "GHSA-9r87-mvcw-x35f",
  "modified": "2026-07-06T20:52:13Z",
  "published": "2026-07-06T20:52:13Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/coder/coder/security/advisories/GHSA-9r87-mvcw-x35f"
    },
    {
      "type": "WEB",
      "url": "https://github.com/coder/coder/pull/25712"
    },
    {
      "type": "WEB",
      "url": "https://github.com/coder/coder/pull/25713"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/coder/coder"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Coder vulnerable to OIDC account takeover via email-based user matching and email_verified bypass"
}


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