diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index c2ff97021ff55c31a6f38f31bf6465f736a4999f..8fe708f001e5bf0213b17c847d2a10ee552fad60 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -29,6 +29,7 @@
 #include "qemu/queue.h"
 #include "qemu/host-utils.h"
 #include "qemu/sockets.h"
+#include "qemu/base64.h"
 
 #ifndef CONFIG_HAS_ENVIRON
 #ifdef __APPLE__
@@ -525,7 +526,10 @@ GuestFileWrite *qmp_guest_file_write(int64_t handle, const char *buf_b64,
         gfh->state = RW_STATE_NEW;
     }
 
-    buf = g_base64_decode(buf_b64, &buf_len);
+    buf = qbase64_decode(buf_b64, -1, &buf_len, errp);
+    if (!buf) {
+        return NULL;
+    }
 
     if (!has_count) {
         count = buf_len;
@@ -1963,7 +1967,10 @@ void qmp_guest_set_user_password(const char *username,
     char *chpasswddata = NULL;
     size_t chpasswdlen;
 
-    rawpasswddata = (char *)g_base64_decode(password, &rawpasswdlen);
+    rawpasswddata = (char *)qbase64_decode(password, -1, &rawpasswdlen, errp);
+    if (!rawpasswddata) {
+        return;
+    }
     rawpasswddata = g_renew(char, rawpasswddata, rawpasswdlen + 1);
     rawpasswddata[rawpasswdlen] = '\0';
 
diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index 0654fe4fe70c7c3e971a7de2f2f72edd9bb67e83..61ffbdf1ee689da3cba590f09cbdde2282006833 100644
--- a/qga/commands-win32.c
+++ b/qga/commands-win32.c
@@ -34,6 +34,7 @@
 #include "qapi/qmp/qerror.h"
 #include "qemu/queue.h"
 #include "qemu/host-utils.h"
+#include "qemu/base64.h"
 
 #ifndef SHTDN_REASON_FLAG_PLANNED
 #define SHTDN_REASON_FLAG_PLANNED 0x80000000
@@ -357,7 +358,10 @@ GuestFileWrite *qmp_guest_file_write(int64_t handle, const char *buf_b64,
         return NULL;
     }
     fh = gfh->fh;
-    buf = g_base64_decode(buf_b64, &buf_len);
+    buf = qbase64_decode(buf_b64, -1, &buf_len, errp);
+    if (!buf) {
+        return NULL;
+    }
 
     if (!has_count) {
         count = buf_len;
@@ -1294,7 +1298,10 @@ void qmp_guest_set_user_password(const char *username,
         return;
     }
 
-    rawpasswddata = (char *)g_base64_decode(password, &rawpasswdlen);
+    rawpasswddata = (char *)qbase64_decode(password, -1, &rawpasswdlen, errp);
+    if (!rawpasswddata) {
+        return;
+    }
     rawpasswddata = g_renew(char, rawpasswddata, rawpasswdlen + 1);
     rawpasswddata[rawpasswdlen] = '\0';
 
diff --git a/qga/commands.c b/qga/commands.c
index bb73e7dfbf27bb9767c6fdd705ce98147e60db23..58568d845230f9cf7ec69d1f3e76fa39eb712e32 100644
--- a/qga/commands.c
+++ b/qga/commands.c
@@ -14,6 +14,7 @@
 #include "qga/guest-agent-core.h"
 #include "qga-qmp-commands.h"
 #include "qapi/qmp/qerror.h"
+#include "qemu/base64.h"
 
 /* Maximum captured guest-exec out_data/err_data - 16MB */
 #define GUEST_EXEC_MAX_OUTPUT (16*1024*1024)
@@ -393,10 +394,19 @@ GuestExec *qmp_guest_exec(const char *path,
     GIOChannel *in_ch, *out_ch, *err_ch;
     GSpawnFlags flags;
     bool has_output = (has_capture_output && capture_output);
+    uint8_t *input = NULL;
+    size_t ninput = 0;
 
     arglist.value = (char *)path;
     arglist.next = has_arg ? arg : NULL;
 
+    if (has_input_data) {
+        input = qbase64_decode(input_data, -1, &ninput, err);
+        if (!input) {
+            return NULL;
+        }
+    }
+
     argv = guest_exec_get_args(&arglist, true);
     envp = has_env ? guest_exec_get_args(env, false) : NULL;
 
@@ -425,7 +435,8 @@ GuestExec *qmp_guest_exec(const char *path,
     g_child_watch_add(pid, guest_exec_child_watch, gei);
 
     if (has_input_data) {
-        gei->in.data = g_base64_decode(input_data, &gei->in.size);
+        gei->in.data = input;
+        gei->in.size = ninput;
 #ifdef G_OS_WIN32
         in_ch = g_io_channel_win32_new_fd(in_fd);
 #else