Vulnerability-Lookup

CVE-2026-55430 (GCVE-0-2026-55430)

Vulnerability from cvelistv5 – Published: 2026-07-08 00:03 – Updated: 2026-07-08 17:10

Title

Coder's subdomain workspace app routing trusts unauthenticated X-Forwarded-Host header, enabling cross-app data access

Summary

Coder allows organizations to provision remote development environments via Terraform. Prior to versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2, the workspace app proxy resolves the target app from `httpapi.RequestHost()` which prefers the `X-Forwarded-Host` header over the real `Host` header. No middleware strips `X-Forwarded-Host` before routing and the header is not browser-forbidden so client-side JavaScript can set it on `fetch()` calls. Practical exploitation requires subdomain app routing (wildcard hostname) enabled, a victim who visits the attacker's shared app and a deployment whose upstream proxy does not strip `X-Forwarded-Host`. The fix in versions 2.29.7, 2.32.7, 2.33.8, and 2.34.2 trusts `X-Forwarded-Host` only from configured trusted proxies and otherwise resolves the routing host from the verified request host. As a workaround, place an upstream reverse proxy that strips or overwrites `X-Forwarded-Host` on untrusted requests.

Severity

5.8 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-345 - Insufficient Verification of Data Authenticity
CWE-441 - Unintended Proxy or Intermediary ('Confused Deputy')

Assigner

GitHub_M

References

6 references

URL	Tags
https://github.com/coder/coder/security/advisorie…	x_refsource_CONFIRM
https://github.com/coder/coder/pull/26204	x_refsource_MISC
https://github.com/coder/coder/releases/tag/v2.29.17	x_refsource_MISC
https://github.com/coder/coder/releases/tag/v2.32.7	x_refsource_MISC
https://github.com/coder/coder/releases/tag/v2.33.8	x_refsource_MISC
https://github.com/coder/coder/releases/tag/v2.34.2	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
coder	coder	Affected: >= 2.34.0, < 2.34.2 Affected: >= 2.33.0, < 2.33.8 Affected: >= 2.30.0, < 2.32.7 Affected: < 2.29.17

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-55430

Vulnerability from fkie_nvd - Published: 2026-07-08 01:16 - Updated: 2026-07-08 19:43

Severity

5.8 (Medium) - CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N
6.8 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/coder/coder/pull/26204	Issue Tracking, Patch
security-advisories@github.com	https://github.com/coder/coder/releases/tag/v2.29.17	Release Notes
security-advisories@github.com	https://github.com/coder/coder/releases/tag/v2.32.7	Release Notes
security-advisories@github.com	https://github.com/coder/coder/releases/tag/v2.33.8	Release Notes
security-advisories@github.com	https://github.com/coder/coder/releases/tag/v2.34.2	Release Notes
security-advisories@github.com	https://github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478w	Patch, Vendor Advisory

Impacted products

Vendor	Product	Version
coder	coder	*
coder	coder	*
coder	coder	*
coder	coder	*

JSON

To clipboard

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          "baseScore": 5.8,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "CHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 1.3,
        "impactScore": 4.0,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      },
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 6.8,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "CHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.3,
        "impactScore": 4.0,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-55430",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-08T16:57:10.249359Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-08T01:16:27.270",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Issue Tracking",
        "Patch"
      ],
      "url": "https://github.com/coder/coder/pull/26204"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/coder/coder/releases/tag/v2.29.17"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/coder/coder/releases/tag/v2.32.7"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/coder/coder/releases/tag/v2.33.8"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/coder/coder/releases/tag/v2.34.2"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "url": "https://github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478w"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-345"
        },
        {
          "lang": "en",
          "value": "CWE-441"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-5G4W-3VW9-478W

Vulnerability from github – Published: 2026-07-06 21:05 – Updated: 2026-07-06 21:05

Summary

Coder's subdomain workspace app routing trusts unauthenticated X-Forwarded-Host header, enabling cross-app data access

Details

Summary

The workspace app proxy resolves the target app from httpapi.RequestHost() which prefers the X-Forwarded-Host header over the real Host header. No middleware strips X-Forwarded-Host before routing and the header is not browser-forbidden so client-side JavaScript can set it on fetch() calls.

Note: Practical exploitation requires subdomain app routing (wildcard hostname) enabled, a victim who visits the attacker's shared app and a deployment whose upstream proxy does not strip X-Forwarded-Host.

Impact

App session cookies are scoped to the wildcard parent domain so the browser attaches them to any app subdomain. An attacker who controls a shared workspace app can serve JavaScript that sends same-site requests with a forged X-Forwarded-Host pointing at a victim's private app. The server routes by the attacker-controlled header but authorizes with the victim's cookie which lets the attacker read the victim's private app responses. Subdomain app routing must be enabled and no upstream proxy may strip X-Forwarded-Host.

Patches

The fix trusts X-Forwarded-Host only from configured trusted proxies and otherwise resolves the routing host from the verified request host.

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

Place an upstream reverse proxy that strips or overwrites X-Forwarded-Host on untrusted requests.

Resources

Fix: #26204

Credits

Coder would like to thank Anthropic's Security Team (ANT-2026-22435) for independently disclosing this issue!

Severity

5.8 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N

Show details on source website

JSON

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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-2026-55430"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-345",
      "CWE-441"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-06T21:05:31Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nThe workspace app proxy resolves the target app from `httpapi.RequestHost()` which prefers the `X-Forwarded-Host` header over the real `Host` header. No middleware strips `X-Forwarded-Host` before routing and the header is not browser-forbidden so client-side JavaScript can set it on `fetch()` calls.\n\n\u003e **Note:** Practical exploitation requires subdomain app routing (wildcard hostname) enabled, a victim who visits the attacker\u0027s shared app and a deployment whose upstream proxy does not strip `X-Forwarded-Host`.\n\n### Impact\n\nApp session cookies are scoped to the wildcard parent domain so the browser attaches them to any app subdomain. An attacker who controls a shared workspace app can serve JavaScript that sends same-site requests with a forged `X-Forwarded-Host` pointing at a victim\u0027s private app. The server routes by the attacker-controlled header but authorizes with the victim\u0027s cookie which lets the attacker read the victim\u0027s private app responses. Subdomain app routing must be enabled and no upstream proxy may strip `X-Forwarded-Host`.\n\n### Patches\n\nThe fix trusts `X-Forwarded-Host` only from configured trusted proxies and otherwise resolves the routing host from the verified request host.\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\nPlace an upstream reverse proxy that strips or overwrites `X-Forwarded-Host` on untrusted requests.\n\n### Resources\n\n- Fix: #26204\n\n### Credits\n\nCoder would like to thank Anthropic\u0027s Security Team (ANT-2026-22435) for independently disclosing this issue!",
  "id": "GHSA-5g4w-3vw9-478w",
  "modified": "2026-07-06T21:05:31Z",
  "published": "2026-07-06T21:05:31Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/coder/coder/security/advisories/GHSA-5g4w-3vw9-478w"
    },
    {
      "type": "WEB",
      "url": "https://github.com/coder/coder/pull/26204"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/coder/coder"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Coder\u0027s subdomain workspace app routing trusts unauthenticated X-Forwarded-Host header, enabling cross-app data access"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-55430 (GCVE-0-2026-55430)

FKIE_CVE-2026-55430

GHSA-5G4W-3VW9-478W

Summary

Impact

Patches

Workarounds

Resources

Credits

Tags

Sightings

Nomenclature