diff --git a/libutils/Unicode.cpp b/libutils/Unicode.cpp
index 5fd9155..6cff0f4 100644
--- a/libutils/Unicode.cpp
+++ b/libutils/Unicode.cpp
@@ -180,7 +180,15 @@
     size_t ret = 0;
     const char32_t *end = src + src_len;
     while (src < end) {
-        ret += utf32_codepoint_utf8_length(*src++);
+        size_t char_len = utf32_codepoint_utf8_length(*src++);
+        if (SSIZE_MAX - char_len < ret) {
+            // If this happens, we would overflow the ssize_t type when
+            // returning from this function, so we cannot express how
+            // long this string is in an ssize_t.
+            android_errorWriteLog(0x534e4554, "37723026");
+            return -1;
+        }
+        ret += char_len;
     }
     return ret;
 }
@@ -440,14 +448,23 @@
     size_t ret = 0;
     const char16_t* const end = src + src_len;
     while (src < end) {
+        size_t char_len;
         if ((*src & 0xFC00) == 0xD800 && (src + 1) < end
                 && (*(src + 1) & 0xFC00) == 0xDC00) {
             // surrogate pairs are always 4 bytes.
-            ret += 4;
+            char_len = 4;
             src += 2;
         } else {
-            ret += utf32_codepoint_utf8_length((char32_t) *src++);
+            char_len = utf32_codepoint_utf8_length((char32_t)*src++);
         }
+        if (SSIZE_MAX - char_len < ret) {
+            // If this happens, we would overflow the ssize_t type when
+            // returning from this function, so we cannot express how
+            // long this string is in an ssize_t.
+            android_errorWriteLog(0x534e4554, "37723026");
+            return -1;
+        }
+        ret += char_len;
     }
     return ret;
 }
diff --git a/libziparchive/zip_archive.cc b/libziparchive/zip_archive.cc
index ad40d42..1be4061 100644
--- a/libziparchive/zip_archive.cc
+++ b/libziparchive/zip_archive.cc
@@ -379,6 +379,22 @@
       return -1;
     }
   }
+
+  uint32_t lfh_start_bytes;
+  if (!archive->mapped_zip.ReadAtOffset(reinterpret_cast<uint8_t*>(&lfh_start_bytes),
+                                        sizeof(uint32_t), 0)) {
+    ALOGW("Zip: Unable to read header for entry at offset == 0.");
+    return -1;
+  }
+
+  if (lfh_start_bytes != LocalFileHeader::kSignature) {
+    ALOGW("Zip: Entry at offset zero has invalid LFH signature %" PRIx32, lfh_start_bytes);
+#if defined(__ANDROID__)
+    android_errorWriteLog(0x534e4554, "64211847");
+#endif
+    return -1;
+  }
+
   ALOGV("+++ zip good scan %" PRIu16 " entries", num_entries);
 
   return 0;
diff --git a/libziparchive/zip_archive_test.cc b/libziparchive/zip_archive_test.cc
index dbc14f0..753bd44 100644
--- a/libziparchive/zip_archive_test.cc
+++ b/libziparchive/zip_archive_test.cc
@@ -717,6 +717,55 @@
   ASSERT_STREQ("I/O error", ErrorCodeString(kIoError));
 }
 
+// A zip file whose local file header at offset zero is corrupted.
+//
+// ---------------
+// cat foo > a.txt
+// zip a.zip a.txt
+// cat a.zip | xxd -i
+//
+// Manual changes :
+// [2] = 0xff  // Corrupt the LFH signature of entry 0.
+// [3] = 0xff  // Corrupt the LFH signature of entry 0.
+static const std::vector<uint8_t> kZipFileWithBrokenLfhSignature{
+    //[lfh-sig-----------], [lfh contents---------------------------------
+    0x50, 0x4b, 0xff, 0xff, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x77, 0x80,
+    //--------------------------------------------------------------------
+    0x09, 0x4b, 0xa8, 0x65, 0x32, 0x7e, 0x04, 0x00, 0x00, 0x00, 0x04, 0x00,
+    //-------------------------------]  [file-name-----------------], [---
+    0x00, 0x00, 0x05, 0x00, 0x1c, 0x00, 0x61, 0x2e, 0x74, 0x78, 0x74, 0x55,
+    // entry-contents------------------------------------------------------
+    0x54, 0x09, 0x00, 0x03, 0x51, 0x24, 0x8b, 0x59, 0x51, 0x24, 0x8b, 0x59,
+    //--------------------------------------------------------------------
+    0x75, 0x78, 0x0b, 0x00, 0x01, 0x04, 0x89, 0x42, 0x00, 0x00, 0x04, 0x88,
+    //-------------------------------------], [cd-record-sig-------], [---
+    0x13, 0x00, 0x00, 0x66, 0x6f, 0x6f, 0x0a, 0x50, 0x4b, 0x01, 0x02, 0x1e,
+    // cd-record-----------------------------------------------------------
+    0x03, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x77, 0x80, 0x09, 0x4b, 0xa8,
+    //--------------------------------------------------------------------
+    0x65, 0x32, 0x7e, 0x04, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x05,
+    //--------------------------------------------------------------------
+    0x00, 0x18, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0xa0,
+    //-]  [lfh-file-header-off-], [file-name-----------------], [extra----
+    0x81, 0x00, 0x00, 0x00, 0x00, 0x61, 0x2e, 0x74, 0x78, 0x74, 0x55, 0x54,
+    //--------------------------------------------------------------------
+    0x05, 0x00, 0x03, 0x51, 0x24, 0x8b, 0x59, 0x75, 0x78, 0x0b, 0x00, 0x01,
+    //-------------------------------------------------------], [eocd-sig-
+    0x04, 0x89, 0x42, 0x00, 0x00, 0x04, 0x88, 0x13, 0x00, 0x00, 0x50, 0x4b,
+    //-------], [---------------------------------------------------------
+    0x05, 0x06, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x4b, 0x00,
+    //-------------------------------------------]
+    0x00, 0x00, 0x43, 0x00, 0x00, 0x00, 0x00, 0x00};
+
+TEST(ziparchive, BrokenLfhSignature) {
+  TemporaryFile tmp_file;
+  ASSERT_NE(-1, tmp_file.fd);
+  ASSERT_TRUE(android::base::WriteFully(tmp_file.fd, &kZipFileWithBrokenLfhSignature[0],
+                                        kZipFileWithBrokenLfhSignature.size()));
+  ZipArchiveHandle handle;
+  ASSERT_EQ(-1, OpenArchiveFd(tmp_file.fd, "LeadingNonZipBytes", &handle));
+}
+
 int main(int argc, char** argv) {
   ::testing::InitGoogleTest(&argc, argv);