diff --git a/src/common/blkreftable.c b/src/common/blkreftable.c
index c16ef736f00..3ef5aeae2b0 100644
--- a/src/common/blkreftable.c
+++ b/src/common/blkreftable.c
@@ -657,6 +657,15 @@ BlockRefTableReaderNextRelation(BlockRefTableReader *reader,
 		return false;
 	}
 
+	/* Sanity-check the fork number. */
+	if (sentry.forknum < 0 || sentry.forknum > MAX_FORKNUM)
+	{
+		reader->error_callback(reader->error_callback_arg,
+							   "file \"%s\" has invalid fork number %d",
+							   reader->error_filename, sentry.forknum);
+		return false;
+	}
+
 	/*
 	 * Sanity-check the nchunks value.  In the backend, palloc_array would
 	 * enforce this anyway (with a more generic error message); but in
@@ -678,6 +687,19 @@ BlockRefTableReaderNextRelation(BlockRefTableReader *reader,
 	BlockRefTableRead(reader, reader->chunk_size,
 					  sentry.nchunks * sizeof(uint16));
 
+	/* Sanity-check the chunk sizes. */
+	for (unsigned i = 0; i < sentry.nchunks; ++i)
+	{
+		if (reader->chunk_size[i] > MAX_ENTRIES_PER_CHUNK)
+		{
+			reader->error_callback(reader->error_callback_arg,
+								   "file \"%s\" chunk %u has invalid size %u",
+								   reader->error_filename, i,
+								   (unsigned) reader->chunk_size[i]);
+			return false;
+		}
+	}
+
 	/* Set up for chunk scan. */
 	reader->total_chunks = sentry.nchunks;
 	reader->consumed_chunks = 0;