diff --git a/verifier.cpp b/verifier.cpp
index 782a838..23fab07 100644
--- a/verifier.cpp
+++ b/verifier.cpp
@@ -79,6 +79,13 @@
     LOGI("comment is %d bytes; signature %d bytes from end\n",
          comment_size, signature_start);
 
+    if (signature_start > comment_size) {
+        LOGE("signature start: %zu is larger than comment size: %zu\n", signature_start,
+             comment_size);
+        fclose(f);
+        return VERIFY_FAILURE;
+    }
+
     if (signature_start - FOOTER_SIZE < RSANUMBYTES) {
         // "signature" block isn't big enough to contain an RSA block.
         LOGE("signature is too short\n");