OrchardCMS/OrchardCore · error · AntivirusScanningException

The ClamAV antivirus scanner failed while scanning

Error message

The ClamAV antivirus scanner failed while scanning '{context.FileName}'.

What it means

IOException during the ClamAV INSTREAM scan is caught in CreatingAsync and rethrown as an AntivirusScanningException with this generic failure message. It indicates a stream/IO failure while transferring the file to or reading the result from the ClamAV daemon.

Solutions

1. Inspect the inner exception (logged via LogError) to find the underlying IO cause.
2. Check clamd's StreamMaxLength / TCPSocket settings — oversized streams can be dropped.
3. Ensure clamd is stable (uptime, memory) and not being restarted mid-upload.
4. Retry the upload; if persistent, check disk space and temp directory health on the app host.

try
{
    await UploadFileAsync(stream);
}
catch (AntivirusScanningException ex) when (ex.InnerException is IOException)
{
    logger.LogError(ex, "IO failure during AV scan; retrying may help.");
    // retry once, then fail the upload cleanly
}

When it happens

Trigger: ScanAsync raises IOException — e.g. the clamd connection drops mid-transfer, the temp seekable stream write/read fails, or the socket stream is broken while scanning context.FileName.

Common situations: clamd restarting mid-scan, connection reset by clamd's StreamMaxLength limit, disk issues with the temp file, flaky network between app and daemon.

Related errors

• The ClamAV antivirus scanner timed out while scanning
• Cannot create a stream for a directory.
• Error retrieving file info for
• Error creating directory
• Error deleting file

AI-assisted analysis of OrchardCMS/OrchardCore@4306c0717f (2026-09-13). Data as JSON: /api/errors/f4b93f6d01168137. Report an issue: GitHub.

Appendix: source

Thrown at src/OrchardCore.Modules/OrchardCore.Antivirus/ClamAV/ClamAvFileEventHandler.cs:88

            if (scanStream != stream)
            {
                await scanStream.DisposeAsync();
            }

            _logger.LogError(exception, "ClamAV could not be reached while scanning '{FileName}'.", context.FileName);

            throw new AntivirusScanningException($"The ClamAV antivirus scanner could not be reached while scanning '{context.FileName}'.", exception);
        }
        catch (IOException exception)
        {
            if (scanStream != stream)
            {
                await scanStream.DisposeAsync();
            }

            _logger.LogError(exception, "ClamAV failed while scanning '{FileName}'.", context.FileName);

            throw new AntivirusScanningException($"The ClamAV antivirus scanner failed while scanning '{context.FileName}'.", exception);
        }
        catch
        {
            if (scanStream != stream)
            {
                await scanStream.DisposeAsync();
            }

            throw;
        }
    }

    public Task CreatedAsync(IFileStoreEntry fileInfo, CancellationToken cancellationToken = default)
        => Task.CompletedTask;

    private async Task<Stream> CreateSeekableStreamAsync(Stream stream, CancellationToken cancellationToken)
    {
        var tempFilePath = _tempDirectoryProvider.GetTempFileName();

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