Vulnerability-Lookup

CVE-2026-34457 (GCVE-0-2026-34457)

Vulnerability from cvelistv5 – Published: 2026-04-14 22:14 – Updated: 2026-04-15 17:43

Title

OAuth2 Proxy: Health Check User-Agent Matching Bypasses Authentication in auth_request Mode

Summary

OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions prior to 7.15.2 contain a configuration-dependent authentication bypass in deployments where OAuth2 Proxy is used with an auth_request-style integration (such as nginx auth_request) and either --ping-user-agent is set or --gcp-healthchecks is enabled. In affected configurations, OAuth2 Proxy treats any request with the configured health check User-Agent value as a successful health check regardless of the requested path, allowing an unauthenticated remote attacker to bypass authentication and access protected upstream resources. Deployments that do not use auth_request-style subrequests or that do not enable --ping-user-agent/--gcp-healthchecks are not affected. This issue is fixed in 7.15.2.

Severity

9.1 (Critical)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-04-15 17:43 UTC

CWE

CWE-290 - Authentication Bypass by Spoofing

Assigner

GitHub_M mitre root

References

2 references

URL	Tags
https://github.com/oauth2-proxy/oauth2-proxy/secu…	x_refsource_CONFIRM
https://github.com/oauth2-proxy/oauth2-proxy/rele…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
oauth2-proxy	oauth2-proxy	Affected: < 7.15.2	guessed

Show details on NVD website

JSON

To clipboard

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                "id": "CVE-2026-34457",
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FKIE_CVE-2026-34457

Vulnerability from fkie_nvd - Published: 2026-04-14 23:16 - Updated: 2026-07-24 22:10

Severity

9.1 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.15.2	Release Notes
	security-advisories@github.com	https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-5hvv-m4w4-gf6v	Mitigation, Vendor Advisory

Impacted products

	Vendor	Product	Version
	oauth2_proxy_project	oauth2_proxy	*

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "oauth2-proxy",
          "vendor": "oauth2-proxy",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 7.15.2"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:oauth2_proxy_project:oauth2_proxy:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "8ECD42F0-BA8D-4BA5-A347-1CAD636DCF70",
              "versionEndExcluding": "7.15.2",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions prior to 7.15.2 contain a configuration-dependent authentication bypass in deployments where OAuth2 Proxy is used with an auth_request-style integration (such as nginx auth_request) and either --ping-user-agent is set or --gcp-healthchecks is enabled. In affected configurations, OAuth2 Proxy treats any request with the configured health check User-Agent value as a successful health check regardless of the requested path, allowing an unauthenticated remote attacker to bypass authentication and access protected upstream resources. Deployments that do not use auth_request-style subrequests or that do not enable --ping-user-agent/--gcp-healthchecks are not affected. This issue is fixed in 7.15.2."
    },
    {
      "lang": "es",
      "value": "OAuth2 Proxy es un proxy inverso que proporciona autenticaci\u00f3n utilizando proveedores OAuth2. Las versiones anteriores a la 7.15.2 contienen una omisi\u00f3n de autenticaci\u00f3n dependiente de la configuraci\u00f3n en implementaciones donde OAuth2 Proxy se utiliza con una integraci\u00f3n de estilo auth_request (como nginx auth_request) y se establece --ping-user-agent o se habilita --gcp-healthchecks. En las configuraciones afectadas, OAuth2 Proxy trata cualquier solicitud con el valor configurado de User-Agent de verificaci\u00f3n de estado como una verificaci\u00f3n de estado exitosa, independientemente de la ruta solicitada, permitiendo a un atacante remoto no autenticado omitir la autenticaci\u00f3n y acceder a recursos ascendentes protegidos. Las implementaciones que no utilizan subsolicitudes de estilo auth_request o que no habilitan --ping-user-agent/--gcp-healthchecks no se ven afectadas. Este problema se soluciona en la 7.15.2."
    }
  ],
  "id": "CVE-2026-34457",
  "lastModified": "2026-07-24T22:10:00.140",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 9.1,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
          "version": "3.1"
        },
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        "impactScore": 5.2,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
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        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
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          "options": [
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              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-04-15T17:43:23.417901Z",
          "version": "2.0.3"
        }
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    ]
  },
  "published": "2026-04-14T23:16:28.330",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.15.2"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Mitigation",
        "Vendor Advisory"
      ],
      "url": "https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-5hvv-m4w4-gf6v"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-290"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-5HVV-M4W4-GF6V

Vulnerability from github – Published: 2026-04-14 22:31 – Updated: 2026-04-15 21:06

Summary

OAuth2 Proxy's Health Check User-Agent Matching Bypasses Authentication in auth_request Mode

Details

Impact

A configuration-dependent authentication bypass exists in OAuth2 Proxy.

Deployments are affected when all of the following are true:

OAuth2 Proxy is used with an auth_request-style integration (for example, nginx auth_request)
--ping-user-agent is set or --gcp-healthchecks is enabled

In affected configurations, OAuth2 Proxy will treat a request with the configured health check User-Agent value as a successful health check regardless of the requested path. This allows an unauthenticated remote attacker to bypass authentication and access protected upstream resources without completing the normal login flow.

This issue does not affect deployments that do not use auth_request-style subrequests, or that do not enable --ping-user-agent/--gcp-healthchecks.

Patches

Users should upgrade to v7.15.2 or later once available. Deployments running versions prior to v7.15.2 should be considered affected if they use auth_request-style authentication together with --ping-user-agent or --gcp-healthchecks.

Workarounds

Users can mitigate this issue by:

disabling --gcp-healthchecks
removing any configured --ping-user-agent
ensuring the reverse proxy does not forward client-controlled User-Agent headers to the OAuth2 Proxy auth subrequest
using path-based health checks only, on dedicated health check endpoints

Example nginx mitigation for the auth subrequest:

location = /oauth2/auth {
    internal;
    proxy_pass http://127.0.0.1:4180;
    proxy_pass_request_body off;
    proxy_set_header Content-Length "";
    proxy_set_header Host $host;
    # set to value that isn't the same as your configured PingUserAgent or GCPs "GoogleHC/1.0"
    proxy_set_header User-Agent "oauth2-proxy-auth-request";
}

Severity

9.1 (Critical)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/oauth2-proxy/oauth2-proxy/v7"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.15.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/oauth2-proxy/oauth2-proxy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "3.2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-34457"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-290"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-14T22:31:19Z",
    "nvd_published_at": "2026-04-14T23:16:28Z",
    "severity": "CRITICAL"
  },
  "details": "### Impact\nA configuration-dependent authentication bypass exists in OAuth2 Proxy.\n\nDeployments are affected when all of the following are true:\n\n- OAuth2 Proxy is used with an `auth_request`-style integration   (for example, nginx `auth_request`)\n- `--ping-user-agent` is set or `--gcp-healthchecks` is enabled\n\nIn affected configurations, OAuth2 Proxy will treat a request with the configured health check `User-Agent` value as a successful health check regardless of the requested path. This allows an unauthenticated remote attacker to bypass authentication and access protected upstream resources without completing the normal login flow.\n\nThis issue does not affect deployments that do not use `auth_request`-style subrequests, or that do not enable  `--ping-user-agent`/`--gcp-healthchecks`.\n\n### Patches\nUsers should upgrade to `v7.15.2` or later once available. Deployments running versions prior to `v7.15.2` should be considered affected if they use `auth_request`-style authentication together with `--ping-user-agent` or  `--gcp-healthchecks`.\n\n### Workarounds\nUsers can mitigate this issue by:\n\n- disabling `--gcp-healthchecks`\n- removing any configured `--ping-user-agent`\n- ensuring the reverse proxy does not forward client-controlled `User-Agent`  headers to the OAuth2 Proxy auth subrequest\n- using path-based health checks only, on dedicated health check endpoints\n\nExample nginx mitigation for the auth subrequest:\n\n```nginx\nlocation = /oauth2/auth {\n    internal;\n    proxy_pass http://127.0.0.1:4180;\n    proxy_pass_request_body off;\n    proxy_set_header Content-Length \"\";\n    proxy_set_header Host $host;\n    # set to value that isn\u0027t the same as your configured PingUserAgent or GCPs \"GoogleHC/1.0\"\n    proxy_set_header User-Agent \"oauth2-proxy-auth-request\";\n}\n```",
  "id": "GHSA-5hvv-m4w4-gf6v",
  "modified": "2026-04-15T21:06:37Z",
  "published": "2026-04-14T22:31:19Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-5hvv-m4w4-gf6v"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34457"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/oauth2-proxy/oauth2-proxy"
    },
    {
      "type": "WEB",
      "url": "https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.15.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": " OAuth2 Proxy\u0027s Health Check User-Agent Matching Bypasses Authentication in auth_request Mode"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Action not permitted

CVE-2026-34457 (GCVE-0-2026-34457)

FKIE_CVE-2026-34457

GHSA-5HVV-M4W4-GF6V

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