diff --git a/fastboot/bootimg_utils.cpp b/fastboot/bootimg_utils.cpp
index c1028ef..62a26b3 100644
--- a/fastboot/bootimg_utils.cpp
+++ b/fastboot/bootimg_utils.cpp
@@ -28,13 +28,15 @@
 
 #include "bootimg_utils.h"
 
+#include "fastboot.h"
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
-void bootimg_set_cmdline(boot_img_hdr* h, const char* cmdline)
-{
-    strcpy((char*) h->cmdline, cmdline);
+void bootimg_set_cmdline(boot_img_hdr* h, const char* cmdline) {
+    if (strlen(cmdline) >= sizeof(h->cmdline)) die("command line too large: %zu", strlen(cmdline));
+    strcpy(reinterpret_cast<char*>(h->cmdline), cmdline);
 }
 
 boot_img_hdr* mkbootimg(void* kernel, int64_t kernel_size, off_t kernel_offset,
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index 6175f59..536d64e 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -447,8 +447,11 @@
     if (kdata == nullptr) die("cannot load '%s': %s", kernel.c_str(), strerror(errno));
 
     // Is this actually a boot image?
+    if (ksize < static_cast<int64_t>(sizeof(boot_img_hdr))) {
+        die("cannot load '%s': too short", kernel.c_str());
+    }
     if (!memcmp(kdata, BOOT_MAGIC, BOOT_MAGIC_SIZE)) {
-        if (cmdline) bootimg_set_cmdline((boot_img_hdr*) kdata, cmdline);
+        if (cmdline) bootimg_set_cmdline(reinterpret_cast<boot_img_hdr*>(kdata), cmdline);
 
         if (!ramdisk.empty()) die("cannot boot a boot.img *and* ramdisk");