diff --git a/usr.bin/etdump/etdump.c b/usr.bin/etdump/etdump.c
--- a/usr.bin/etdump/etdump.c
+++ b/usr.bin/etdump/etdump.c
@@ -116,8 +116,8 @@
 }
 
 static int
-dump_section(char *buffer, size_t offset, FILE *outfile, const char *filename,
-    struct outputter *outputter)
+dump_section(char *buffer, size_t bufsize, size_t offset, FILE *outfile,
+    const char *filename, struct outputter *outputter)
 {
 	boot_catalog_section_header *sh;
 	u_char platform_id;
@@ -125,6 +125,8 @@
 	size_t entry_offset;
 	boot_catalog_section_entry *entry;
 
+	if (offset + sizeof(boot_catalog_section_header) > bufsize)
+		errx(1, "%s: section header out of bounds", filename);
 	sh = (boot_catalog_section_header *)&buffer[offset];
 	if (outputter->output_section != NULL) {
 		outputter->output_section(outfile, filename, sh);
@@ -135,6 +137,10 @@
 	if (outputter->output_entry != NULL) {
 		for (i = 1; i <= (int)sh->num_section_entries[0]; i++) {
 			entry_offset = offset + i * ET_BOOT_ENTRY_SIZE;
+			if (entry_offset + sizeof(boot_catalog_section_entry) >
+			    bufsize)
+				errx(1, "%s: section entry out of bounds",
+				    filename);
 			entry =
 			    (boot_catalog_section_entry *)&buffer[entry_offset];
 			outputter->output_entry(outfile, filename, entry,
@@ -195,8 +201,8 @@
 		    (uint8_t)entry[0] != ET_SECTION_HEADER_LAST)
 			break;
 
-		entry_count = dump_section(buffer, offset, outfile, filename,
-		    outputter);
+		entry_count = dump_section(buffer, sizeof(buffer), offset,
+		    outfile, filename, outputter);
 
 		offset += entry_count * ET_BOOT_ENTRY_SIZE;
 	}