AccessViolationException and Heap Corruption in SQLGetData during ETL operations on Windows

[agourbeyre-MyReport]

AccessViolationException and Heap Corruption in SQLGetData during ETL operations on Windows

Environment

Component	Version
ODBC Driver	Amazon Redshift ODBC v2.1.8.0 and v2.1.12.0 (64-bit) - tested both
aws-sdk-cpp	1.11.598 (v2.1.8) / 1.11.711 (v2.1.12)
OpenSSL	1.1.1zb / 1.1.1zd
OS	Windows Server 2019 Standard
.NET Runtime	.NET 8.0.11, CoreCLR 8.0.1124.51707
Redshift endpoint	pennylane-external.csqwamh5pldr.eu-west-1.redshift.amazonaws.com:5439

DSN Configuration

Database: Prod
Auth Type: Standard
SSL Mode: verify-ca
Min TLS: 1.2
Proxy: None
Cursor Size: 20000 (also tested with 1000 - same issue)
Advanced Options:
  - Autofetch Refcursors: Enabled
  - Rollback on Error: Enabled
  - Database Metadata Current Database: Enabled
Retry Delay: 3

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Description

Expected behavior:
ODBC driver should reliably return data from Redshift queries without memory corruption during sustained ETL operations.

Observed behavior:
The ODBC driver causes the host application to crash with memory corruption errors:

1. System.AccessViolationException in SQLGetData native interop
2. STATUS_HEAP_CORRUPTION (0xc0000374) in ntdll.dll

The crashes are intermittent - ETL jobs sometimes complete successfully, other times crash mid-extraction on different tables. This suggests a race condition or memory management issue in the native driver code.

Impact:
Production ETL services crash unexpectedly, blocking data pipelines. Multiple independent customers are affected.

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Steps to reproduce

1. Configure ODBC DSN with Amazon Redshift driver v2.1.12.0 on Windows Server 2019
2. Connect to Redshift cluster using Standard authentication with SSL (verify-ca)
3. Execute multiple sequential SELECT queries extracting data from various tables
4. Process results using SQLGetData to retrieve column values (especially strings)
5. Run ETL jobs on schedule (e.g., every hour) with cursor size 20000

The crash typically occurs:

• During multi-table extraction workflows
• When reading string column data via SQLGetData
• Intermittently - not always on the same table

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Error messages / Stack traces

Error 1: AccessViolationException (Windows Event Log)

Application: ServerMyReport.exe
CoreCLR Version: 8.0.1124.51707
.NET Version: 8.0.11
Description: The process was terminated due to an unhandled exception.

Exception Info: System.AccessViolationException: Attempted to read or write
protected memory. This is often an indication that other memory is corrupt.

Stack:
  at Interop+Odbc.SQLGetData(OdbcStatementHandle, UInt16, SQL_C, CNativeBuffer, IntPtr, IntPtr ByRef)
  at System.Data.Odbc.OdbcDataReader.GetData(Int32, SQL_C, Int32, Int32 ByRef)
  at System.Data.Odbc.OdbcDataReader.internalGetString(Int32)
  at System.Data.Odbc.OdbcDataReader.GetValue(Int32, TypeMap)
  at System.Data.Odbc.OdbcDataReader.GetValue(Int32)
  [...application code...]

Error 2: Heap Corruption (Windows Event Log)

Exception Code: 0xc0000374 (STATUS_HEAP_CORRUPTION)
Faulting Module: ntdll.dll

ODBC Driver Log (redshift_odbc.log)

Recurring empty error messages observed across 6+ months:

[ERROR] 2026-01-27 16:39:59.496 [RSLIBPQ:rslibpq.c:472] [11896] pError=
[ERROR] 2026-01-27 16:39:41.242 [RSLIBPQ:rslibpq.c:472] [6540] pError=
[ERROR] 2026-01-27 15:43:50.676 [RSLIBPQ:rslibpq.c:472] [6244] pError=
...

Note: The error message after pError= is empty, which appears to be a logging issue in the driver.

Also observed streaming cursor operations before crashes:

[INFO] 2026-01-27 11:18:33.614 [RSUTIL:rsutil.c:10574] Skiping current result for streaming cursor...
[INFO] 2026-01-27 11:18:33.614 [RSUTIL:rsutil.c:10584] Skiping current result for streaming cursor done.iSocketError=0

(Note: "Skiping" appears to be a typo in the driver source code)

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Workarounds tried (all unsuccessful)

Workaround	Result
Upgraded driver from v2.1.8.0 to v2.1.12.0	Still crashes
Reduced cursor size from 20000 to 1000	Still crashes
Limited to 1 CPU / 1 concurrent ETL query	Still crashes
Ensured proper Dispose of ODBC resources in .NET code	Still crashes

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Additional context

• Two independent customers experiencing identical symptoms on different infrastructures
• The crash occurs in native ODBC driver code (SQLGetData), not in the managed .NET layer
• Both AccessViolationException and STATUS_HEAP_CORRUPTION indicate memory corruption in native code
• Issue persists across driver versions (v2.1.8.0 and v2.1.12.0)
• The intermittent nature and different failing tables suggest a race condition, buffer overflow, or use-after-free bug
• ODBC log shows empty pError= messages - possible logging bug masking the actual error

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Attachments

• redshift_odbc.log - Driver trace log spanning July 2025 to January 2026

redshift_odbc.log