diff --git a/src/boot/efi/bcd.c b/src/boot/efi/bcd.c
index 970c8b1c8ec..44c544f8f71 100644
--- a/src/boot/efi/bcd.c
+++ b/src/boot/efi/bcd.c
@@ -19,6 +19,7 @@
 #  define UINT32 uint32_t
 #  define UINT64 uint64_t
 #  define UINTN size_t
+#  define strlena(s) strlen(s)
 #  define strncaseeqa(a, b, n) strncaseeq((a), (b), (n))
 #  define TEST_STATIC static
 #endif
@@ -117,14 +118,14 @@ static const Key *get_subkey(const UINT8 *bcd, UINT32 bcd_len, UINT32 offset, co
         assert(bcd);
         assert(name);
 
-        if ((UINT64) offset + sizeof(SubkeyFast) > bcd_len)
+        if ((UINT64) offset + sizeof(SubkeyFast) >= bcd_len)
                 return NULL;
 
         const SubkeyFast *subkey = (const SubkeyFast *) (bcd + offset);
         if (subkey->sig != SIG_SUBKEY_FAST)
                 return NULL;
 
-        if ((UINT64) offset + offsetof(SubkeyFast, entries) + sizeof(struct SubkeyFastEntry[subkey->n_entries]) > bcd_len)
+        if ((UINT64) offset + offsetof(SubkeyFast, entries) + sizeof(struct SubkeyFastEntry[subkey->n_entries]) >= bcd_len)
                 return NULL;
 
         for (UINT16 i = 0; i < subkey->n_entries; i++) {
@@ -146,18 +147,18 @@ static const Key *get_key(const UINT8 *bcd, UINT32 bcd_len, UINT32 offset, const
         assert(bcd);
         assert(name);
 
-        if ((UINT64) offset + sizeof(Key) > bcd_len)
+        if ((UINT64) offset + sizeof(Key) >= bcd_len)
                 return NULL;
 
         const Key *key = (const Key *) (bcd + offset);
         if (key->sig != SIG_KEY)
                 return NULL;
 
-        if ((UINT64) offset + offsetof(Key, key_name) + sizeof(CHAR8[key->key_name_len]) > bcd_len)
+        if ((UINT64) offset + offsetof(Key, key_name) + sizeof(CHAR8[key->key_name_len]) >= bcd_len)
                 return NULL;
 
         if (*name) {
-                if (strncaseeqa(name, key->key_name, key->key_name_len) && !name[key->key_name_len])
+                if (strncaseeqa(name, key->key_name, key->key_name_len) && strlena(name) == key->key_name_len)
                         name += key->key_name_len;
                 else
                         return NULL;
@@ -175,21 +176,21 @@ static const KeyValue *get_key_value(const UINT8 *bcd, UINT32 bcd_len, const Key
         if (key->n_key_values == 0)
                 return NULL;
 
-        if ((UINT64) key->key_values_offset + sizeof(UINT32[key->n_key_values]) > bcd_len)
+        if ((UINT64) key->key_values_offset + sizeof(UINT32[key->n_key_values]) >= bcd_len)
                 return NULL;
 
         const UINT32 *key_value_list = (const UINT32 *) (bcd + key->key_values_offset);
         for (UINT32 i = 0; i < key->n_key_values; i++) {
                 UINT32 offset = *(key_value_list + i);
 
-                if ((UINT64) offset + sizeof(KeyValue) > bcd_len)
+                if ((UINT64) offset + sizeof(KeyValue) >= bcd_len)
                         continue;
 
                 const KeyValue *kv = (const KeyValue *) (bcd + offset);
                 if (kv->sig != SIG_KEY_VALUE)
                         continue;
 
-                if ((UINT64) offset + offsetof(KeyValue, name) + kv->name_len > bcd_len)
+                if ((UINT64) offset + offsetof(KeyValue, name) + kv->name_len >= bcd_len)
                         continue;
 
                 /* If most significant bit is set, data is stored in data_offset itself, but
@@ -198,10 +199,10 @@ static const KeyValue *get_key_value(const UINT8 *bcd, UINT32 bcd_len, const Key
                 if (FLAGS_SET(kv->data_size, UINT32_C(1) << 31))
                         continue;
 
-                if ((UINT64) kv->data_offset + kv->data_size > bcd_len)
+                if ((UINT64) kv->data_offset + kv->data_size >= bcd_len)
                         continue;
 
-                if (strncaseeqa(name, kv->name, kv->name_len) && !name[kv->name_len])
+                if (strncaseeqa(name, kv->name, kv->name_len) && strlena(name) == kv->name_len)
                         return kv;
         }
 
@@ -228,7 +229,7 @@ static const KeyValue *get_key_value(const UINT8 *bcd, UINT32 bcd_len, const Key
 TEST_STATIC CHAR16 *get_bcd_title(UINT8 *bcd, UINTN bcd_len) {
         assert(bcd);
 
-        if (HIVE_CELL_OFFSET > bcd_len)
+        if (HIVE_CELL_OFFSET >= bcd_len)
                 return NULL;
 
         BaseBlock *base_block = (BaseBlock *) bcd;
@@ -316,6 +317,6 @@ TEST_STATIC CHAR16 *get_bcd_title(UINT8 *bcd, UINTN bcd_len) {
 
         /* The data should already be NUL-terminated. */
         CHAR16 *title = (CHAR16 *) (bcd + description_value->data_offset);
-        title[description_value->data_size / sizeof(CHAR16)] = '\0';
+        title[description_value->data_size / sizeof(CHAR16) - 1] = '\0';
         return title;
 }
diff --git a/src/boot/efi/util.c b/src/boot/efi/util.c
index 6db4ab39695..76e4eef1eb5 100644
--- a/src/boot/efi/util.c
+++ b/src/boot/efi/util.c
@@ -174,7 +174,7 @@ EFI_STATUS efivar_get(const EFI_GUID *vendor, const CHAR16 *name, CHAR16 **value
                 return EFI_SUCCESS;
 
         /* Return buffer directly if it happens to be NUL terminated already */
-        if (size >= sizeof(CHAR16) && buf[size/sizeof(CHAR16)] == 0) {
+        if (size >= sizeof(CHAR16) && buf[size / sizeof(CHAR16) - 1] == 0) {
                 *value = TAKE_PTR(buf);
                 return EFI_SUCCESS;
         }
@@ -183,7 +183,7 @@ EFI_STATUS efivar_get(const EFI_GUID *vendor, const CHAR16 *name, CHAR16 **value
         val = xallocate_pool(size + sizeof(CHAR16));
 
         CopyMem(val, buf, size);
-        val[size / sizeof(CHAR16)] = 0; /* NUL terminate */
+        val[size / sizeof(CHAR16) - 1] = 0; /* NUL terminate */
 
         *value = val;
         return EFI_SUCCESS;