jackc/pgx · error

SCRAM iteration count from server too high

Error message

SCRAM iteration count from server too high: %d (max %d)

What it means

The server's SCRAM iteration count exceeds the client's safety ceiling. This guard prevents a malicious server from forcing the client to burn unbounded CPU in PBKDF2 derivation. PostgreSQL defaults to 4096 iterations; values far above that are rejected.

Solutions

1. Check the server's scram_iterations setting; reset it to a sane value (e.g. 4096)
2. Verify you are connecting to a trusted server
3. Do not blindly raise the client limit; the server may be malicious
4. Report the server configuration to your DBA

When it happens

Trigger: Thrown at pgconn/auth_scram.go:292 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of jackc/pgx@ec1a0befd2 (2026-08-04). Data as JSON: /api/errors/05407baaf8d26eb2. Report an issue: GitHub.

Appendix: source

Thrown at pgconn/auth_scram.go:292

	buf = buf[2:]
	iterationsStr := buf

	var err error
	sc.salt, err = base64.StdEncoding.DecodeString(string(saltStr))
	if err != nil {
		return fmt.Errorf("invalid SCRAM salt received from server: %w", err)
	}

	sc.iterations, err = strconv.Atoi(string(iterationsStr))
	if err != nil || sc.iterations <= 0 {
		return fmt.Errorf("invalid SCRAM iteration count received from server: %w", err)
	}
	// Bound server-supplied iteration count to prevent a malicious server from forcing the client
	// to spend unbounded CPU in PBKDF2. PostgreSQL's scram_iterations defaults to 4096; this ceiling
	// is ~2500x that.
	const maxScramIterations = 10_000_000
	if sc.iterations > maxScramIterations {
		return fmt.Errorf("SCRAM iteration count from server too high: %d (max %d)", sc.iterations, maxScramIterations)
	}

	if !bytes.HasPrefix(sc.clientAndServerNonce, sc.clientNonce) {
		return errors.New("invalid SCRAM nonce: did not start with client nonce")
	}

	if len(sc.clientAndServerNonce) <= len(sc.clientNonce) {
		return errors.New("invalid SCRAM nonce: did not include server nonce")
	}

	return nil
}

func (sc *scramClient) clientFinalMessage() string {
	// The c= attribute carries the base64-encoded channel binding input.
	//
	// Without channel binding this is just the GS2 header alone ("biws" for
	// "n,," or "eSws" for "y,,").

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