--- /dev/null
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Hector Marco-Gisbert <hecmargi@upv.es>
+Date: Fri, 13 Nov 2015 16:21:09 +0100
+Subject: [PATCH] Fix security issue when reading username and password
+
+ This patch fixes two integer underflows at:
+ * grub-core/lib/crypto.c
+ * grub-core/normal/auth.c
+
+Resolves: CVE-2015-8370
+
+Signed-off-by: Hector Marco-Gisbert <hecmargi@upv.es>
+Signed-off-by: Ismael Ripoll-Ripoll <iripoll@disca.upv.es>
+---
+ grub-core/lib/crypto.c | 2 +-
+ grub-core/normal/auth.c | 2 +-
+ 2 files changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/grub-core/lib/crypto.c b/grub-core/lib/crypto.c
+index ca334d5a40e..e6c78d16d39 100644
+--- a/grub-core/lib/crypto.c
++++ b/grub-core/lib/crypto.c
+@@ -468,7 +468,7 @@ grub_password_get (char buf[], unsigned buf_size)
+ break;
+ }
+
+- if (key == '\b')
++ if (key == '\b' && cur_len)
+ {
+ if (cur_len)
+ cur_len--;
+diff --git a/grub-core/normal/auth.c b/grub-core/normal/auth.c
+index 6be678c0de1..c35ce972473 100644
+--- a/grub-core/normal/auth.c
++++ b/grub-core/normal/auth.c
+@@ -172,7 +172,7 @@ grub_username_get (char buf[], unsigned buf_size)
+ break;
+ }
+
+- if (key == GRUB_TERM_BACKSPACE)
++ if (key == GRUB_TERM_BACKSPACE && cur_len)
+ {
+ if (cur_len)
+ {