{
    "document": {
        "category": "csaf_base",
        "csaf_version": "2.0",
        "distribution": {
            "tlp": {
                "label": "WHITE"
            }
        },
        "lang": "en",
        "notes": [
            {
                "category": "legal_disclaimer",
                "text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this portal to enhance access to its information and vulnerabilities. The use of this information is subject to the following terms and conditions:\n\nThe vulnerabilities disclosed in this portal are gathered by NCSC-NL from a variety of open sources, which the user can retrieve from other platforms. NCSC-NL makes every reasonable effort to ensure that the content of this portal is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or real-time keeping up-to-date. NCSC-NL does not control nor guarantee the accuracy, relevance, timeliness or completeness of information obtained from these external sources. The vulnerabilities disclosed in this portal are intended solely for the convenience of professional parties to take appropriate measures to manage the risks posed to the cybersecurity. No rights can be derived from the information provided therein.\n\nNCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of the vulnerabilities disclosed in this portal. This includes damage resulting from the inaccuracy of incompleteness of the information contained in it.\nThe information on this page is subject to Dutch law. All disputes related to or arising from the use of this portal regarding the disclosure of vulnerabilities will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings."
            }
        ],
        "publisher": {
            "category": "coordinator",
            "contact_details": "cert@ncsc.nl",
            "name": "National Cyber Security Centre",
            "namespace": "https://www.ncsc.nl/"
        },
        "title": "CVE-2026-34969",
        "tracking": {
            "current_release_date": "2026-04-02T00:08:42.237329Z",
            "generator": {
                "date": "2026-02-17T15:00:00Z",
                "engine": {
                    "name": "V.E.L.M.A",
                    "version": "1.7"
                }
            },
            "id": "CVE-2026-34969",
            "initial_release_date": "2026-04-01T23:55:50.707801Z",
            "revision_history": [
                {
                    "date": "2026-04-01T23:55:50.707801Z",
                    "number": "1",
                    "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (3).| CWES updated (1)."
                },
                {
                    "date": "2026-04-01T23:55:52.400910Z",
                    "number": "2",
                    "summary": "NCSC Score created."
                }
            ],
            "status": "interim",
            "version": "2"
        }
    },
    "vulnerabilities": [
        {
            "cve": "CVE-2026-34969",
            "cwe": {
                "id": "CWE-598",
                "name": "Use of GET Request Method With Sensitive Query Strings"
            },
            "notes": [
                {
                    "category": "description",
                    "text": "# Refresh Token Leaked via URL Query Parameter in OAuth Provider Callback\n\n## Summary\n\nThe auth service's OAuth provider callback flow places the refresh token directly into the redirect URL as a query parameter. Refresh tokens in URLs are logged in browser history, server access logs, HTTP Referer headers, and proxy/CDN logs.\n\nNote that the refresh token is one-time use and all of these leak vectors are on owned infrastructure or services integrated by the application developer.\n\n## Affected Component\n\n- **Repository**: `github.com/nhost/nhost`\n- **Service**: `services/auth`\n- **File**: `services/auth/go/controller/sign_in_provider_callback_get.go`\n- **Function**: `signinProviderProviderCallback` (lines 257-261)\n\n## Root Cause\n\nIn `sign_in_provider_callback_get.go:257-261`, after successful OAuth sign-in, the refresh token is appended as a URL query parameter:\n\n```go\nif session != nil {\n    values := redirectTo.Query()\n    values.Add(\"refreshToken\", session.RefreshToken)\n    redirectTo.RawQuery = values.Encode()\n}\n```\n\nThis results in a redirect like:\n```\nHTTP/1.1 302 Found\nLocation: https://myapp.com/callback?refreshToken=a1b2c3d4-e5f6-7890-abcd-ef1234567890\n```\n\n## Proof of Concept\n\n### Step 1: Initiate OAuth login\n```\nGET /signin/provider/github?redirectTo=https://myapp.com/callback\n```\n\n### Step 2: Complete OAuth flow with provider\n\n### Step 3: Auth service redirects with token in URL\n```\nHTTP/1.1 302 Found\nLocation: https://myapp.com/callback?refreshToken=a1b2c3d4-e5f6-7890-abcd-ef1234567890\n```\n\n### Step 4: Token is now visible in owned infrastructure and services:\n\n**Browser History:**\n```\n# User's browser history now contains the refresh token\n```\n\n**HTTP Referer Header:**\n```\n# If the callback page loads ANY external resource (image, script, etc.):\nGET /resource.js HTTP/1.1\nHost: cdn.example.com\nReferer: https://myapp.com/callback?refreshToken=a1b2c3d4-e5f6-...\n# Note: modern browsers default to strict-origin-when-cross-origin policy,\n# which strips query parameters from cross-origin Referer headers.\n# Additionally, the Referer is only sent to services integrated by the\n# application developer (analytics, CDNs, etc.), not arbitrary third parties.\n```\n\n**Server Access Logs:**\n```\n# Reverse proxy, CDN, or load balancer logs on owned infrastructure:\n2026-03-08 12:00:00 GET /callback?refreshToken=a1b2c3d4-e5f6-... 200\n```\n\n### Step 5: Attacker uses stolen refresh token\n```bash\n# Exchange stolen refresh token for new access token\ncurl -X POST https://auth.nhost.run/v1/token \\\n  -H 'Content-Type: application/json' \\\n  -d '{\"refreshToken\": \"a1b2c3d4-e5f6-7890-abcd-ef1234567890\"}'\n\n# Note: refresh tokens are one-time use, so this only works if the\n# legitimate client has not already consumed the token and if the attacker has\n# compromised your infrastructure to get access to this information\n```\n\n## Impact\n\n1. **Session Hijacking**: Anyone who obtains the token before it is consumed by the legitimate client can generate new access tokens, though the refresh token is one-time use and cannot be reused after consumption.\n\n2. **Leak Vectors**: URL query parameters are visible in owned infrastructure and integrated services:\n   - Browser history (local access)\n   - HTTP Referer headers (mitigated by modern browser default referrer policies; only sent to developer-integrated services)\n   - Server access logs (owned infrastructure)\n   - Proxy/CDN/WAF logs (owned infrastructure)\n\n3. **Affects All OAuth Providers**: Every OAuth provider flow (GitHub, Google, Apple, etc.) goes through the same callback handler.\n\n## Fix\n\nImplemented PKCE (Proof Key for Code Exchange) for the OAuth flow. With PKCE, the authorization code cannot be exchanged without the `code_verifier` that only the original client possesses, preventing token misuse even if the URL is logged.\n\nSee: https://docs.nhost.io/products/auth/pkce/\n\n## Resources\n\n- OWASP: Session Management - Token Transport: \"Session tokens should not be transported in the URL\"\n- RFC 6749 Section 10.3: \"Access tokens and refresh tokens MUST NOT be included in the redirect URI\"\n- CWE-598: Use of GET Request Method With Sensitive Query Strings\n- CWE-200: Exposure of Sensitive Information to an Unauthorized Actor",
                    "title": "github - https://api.github.com/advisories/GHSA-g2qj-prgh-4g9r"
                },
                {
                    "category": "other",
                    "text": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N",
                    "title": "CVSSV4"
                },
                {
                    "category": "other",
                    "text": "2.3",
                    "title": "CVSSV4 base score"
                },
                {
                    "category": "other",
                    "text": "4.1",
                    "title": "NCSC Score"
                },
                {
                    "category": "other",
                    "text": "Is related to an uncommon cwe id",
                    "title": "NCSC Score top increasing factors"
                }
            ],
            "references": [
                {
                    "category": "external",
                    "summary": "Source - github",
                    "url": "https://api.github.com/advisories/GHSA-g2qj-prgh-4g9r"
                },
                {
                    "category": "external",
                    "summary": "Reference - github",
                    "url": "https://github.com/nhost/nhost/security/advisories/GHSA-g2qj-prgh-4g9r"
                },
                {
                    "category": "external",
                    "summary": "Reference - github",
                    "url": "https://docs.nhost.io/products/auth/pkce"
                },
                {
                    "category": "external",
                    "summary": "Reference - github",
                    "url": "https://github.com/advisories/GHSA-g2qj-prgh-4g9r"
                }
            ],
            "title": "CVE-2026-34969"
        }
    ]
}