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Shared Pooler Certificate Chain Fails Strict TLS Verification: Intermediate CA Missing Key Usage

The Supabase hosted shared transaction pooler at aws-1-eu-west-2.pooler.supabase.com:6543 presents a certificate chain where the intermediate CA ('Supabase Intermediate 2021 CA') lacks a Key Usage extension. Python 3.13 enables VERIFY_X509_STRICT by default in ssl.create_default_context(), causing certificate verification to fail with error 92 at depth 1. This prevents database connections using asyncpg 0.31.0 and OpenSSL 3.6.3, even when the correct root CA is trusted. The issue is reproducible without credentials and occurs before authentication.

highConfidence 92%Python Affected VPython 3.13.5 Affected Vasyncpg 0.31.0 Affected VOpenSSL 3.6.3

Origin Analysis

The intermediate CA certificate, issued by 'Supabase Root 2021 CA', has Basic Constraints CA:TRUE but is missing the required Key Usage extension. Python 3.13's default SSL context enables VERIFY_X509_STRICT, which enforces RFC 5280 conformance and rejects CAs without a Key Usage extension.

1. Download prod-ca-2021.crt from the Supabase dashboard. 2. Ensure OpenSSL 3.6.3 and Python 3.13 with asyncpg 0.31.0 are installed. 3. Run: openssl s_client -starttls postgres -connect aws-1-eu-west-2.pooler.supabase.com:6543 -servername aws-1-eu-west-2.pooler.supabase.com -verify_hostname aws-1-eu-west-2.pooler.supabase.com -CAfile ./prod-ca-2021.crt -no-CApath -no-CAstore -x509_strict -trusted_first -partial_chain -purpose sslserver -auth_level 2 -min_protocol TLSv1.2 -verify_return_error -showcerts </dev/null 4. Observe verification error 92 at depth 1: 'CA cert does not include key usage extension'. 5. Alternatively, use Python asyncpg with default SSL context to reproduce CERTIFICATE_VERIFY_FAILED.

Fixing Code Block

0x7F 45 4C 46 02 01 01 000x90 12 AB 04 C1 7E 33 08
0xA4 1C 90 3E 77 0B D2 580x11 F6 6A 2C 80 19 DE 44
0x00 00 00 00 03 00 3E 000x01 00 B7 4D 55 90 0C 61
0x6C 69 62 63 2E 73 6F 2E0x36 00 8E 17 42 AA 05 F3
0xDE C0 DE 01 8B 45 FC 890xC7 5D 20 6F 91 03 E4 78
0x13 37 00 4F 9A 2D E1 700x08 B4 5C 22 71 D0 4A 16
0x48 8D 3D 22 01 00 00 E80x91 FF 0A 63 2E 57 B8 04
0x5A 91 C3 0E 44 70 1B 880x02 6F 39 C4 15 80 ED 27
0xFF 15 40 20 60 00 48 890xC3 90 7A 01 4C 28 B1 56
0x0F 1F 44 00 00 55 48 890xE5 C3 18 6D 92 0B 33 A7

Edge Case Audit

Disabling VERIFY_X509_STRICT relaxes multiple certificate-conformance checks, not just the missing Key Usage condition. It may mask other certificate issues (e.g., malformed extensions, invalid policies). This workaround should be temporary; the proper fix is for Supabase to reissue the intermediate CA with appropriate Key Usage. Rollback: remove the verify_flags modification to restore strict verification; if the server certificate is later fixed, this code remains harmless but unnecessary.