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Postgres Crashes On Permission Denied For RPC Functions Due To Exit_on_error Misconfiguration

Calling an RPC function without EXECUTE privilege for the anonymous role causes a backend crash and database restart in Supabase's Postgres 17.6.1.111, allowing unauthenticated denial-of-service. The crash is caused by the PostgreSQL configuration parameter exit_on_error being enabled, which forces the backend to terminate on any ERROR instead of returning a normal error response.

criticalConfidence 75%Postgres Affected V17.6.1.111

Origin Analysis

The PostgreSQL configuration parameter exit_on_error is set to on in Supabase's patched build (17.6.1.111). This causes any ERROR, including permission denied for function execution, to terminate the backend process immediately instead of raising a catchable exception. As a result, a simple permission check failure crashes the entire Postgres instance.

1. Create a Postgres function without granting EXECUTE to the anon role. 2. Call that function via the Supabase REST API using only the public anon key (no auth session). 3. Observe that the Postgres backend crashes and the database restarts (~10 seconds downtime). 4. Check the PostgreSQL configuration: SHOW exit_on_error; it returns 'on'.

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

Changing exit_on_error from on to off is a low-risk change and is the default behaviour in standard PostgreSQL. However, if any application or monitoring system was intentionally relying on backend termination on error (which is extremely unusual and not recommended), it would be affected. Rollback: ALTER SYSTEM SET exit_on_error = on; SELECT pg_reload_conf();. Note that existing connections will retain the old setting until they reconnect; a full restart may be required if immediate effect is needed.