diff --git a/src/gdb_packet.c b/src/gdb_packet.c
index f738996..0396e0d 100644
--- a/src/gdb_packet.c
+++ b/src/gdb_packet.c
@@ -120,7 +120,7 @@ void gdb_putpacket(const char *packet, int size)
 			}
 		}
 		gdb_if_putchar('#', 0);
-		sprintf(xmit_csum, "%02X", csum);
+		snprintf(xmit_csum, sizeof(xmit_csum), "%02X", csum);
 		gdb_if_putchar(xmit_csum[0], 0);
 		gdb_if_putchar(xmit_csum[1], 1);
 #ifdef DEBUG_GDBPACKET
diff --git a/src/target/efm32.c b/src/target/efm32.c
index fff186b..4405d99 100644
--- a/src/target/efm32.c
+++ b/src/target/efm32.c
@@ -611,7 +611,7 @@ bool efm32_probe(target *t)
 	uint32_t ram_size   = ram_kib   * 0x400;
 	uint32_t flash_page_size = device->flash_page_size;
 
-	sprintf(variant_string, "%c\b%c\b%s %d F%d %s",
+	snprintf(variant_string, sizeof(variant_string), "%c\b%c\b%s %d F%d %s",
 			di_version + 48, (uint8_t)device_index + 32,
 			device->name, part_number, flash_kib, device->description);
 
diff --git a/src/target/samd.c b/src/target/samd.c
index 13e97fd..3117f2a 100644
--- a/src/target/samd.c
+++ b/src/target/samd.c
@@ -390,15 +390,15 @@ bool samd_probe(target *t)
 
 	/* Part String */
 	if (protected) {
-		sprintf(variant_string,
-		        "Atmel SAMD%d%c%dA%s (rev %c) (PROT=1)",
-		        samd.series, samd.pin, samd.mem,
-		        samd.package, samd.revision);
+		snprintf(variant_string, sizeof(variant_string),
+		         "Atmel SAMD%d%c%dA%s (rev %c) (PROT=1)",
+		         samd.series, samd.pin, samd.mem,
+		         samd.package, samd.revision);
 	} else {
-		sprintf(variant_string,
-		        "Atmel SAMD%d%c%dA%s (rev %c)",
-		        samd.series, samd.pin, samd.mem,
-		        samd.package, samd.revision);
+		snprintf(variant_string, sizeof(variant_string),
+		         "Atmel SAMD%d%c%dA%s (rev %c)",
+		         samd.series, samd.pin, samd.mem,
+		         samd.package, samd.revision);
 	}
 
 	/* Setup Target */