diff -Nru glib2.0-2.64.6/debian/changelog glib2.0-2.64.6/debian/changelog
--- glib2.0-2.64.6/debian/changelog	2021-03-12 16:38:38.000000000 +0000
+++ glib2.0-2.64.6/debian/changelog	2021-07-12 14:56:16.000000000 +0000
@@ -1,3 +1,14 @@
+glib2.0 (2.64.6-1~ubuntu20.04.4) focal; urgency=medium
+
+  * Initialise memory used for file builder buffers to zero, since memory
+    artifacts found themseleves into gschema.compiled files, leading to glib
+    being unable to parse the gschema.compiled files, causing gdm, gnome-shell
+    and various gnome applications to fail to
+    start. (LP: #1930359)
+      - d/p/gvdb-builder-Initialise-some-memory-to-zero-in-the-bloom-.patch
+
+ -- Matthew Ruffell <matthew.ruffell@canonical.com>  Mon, 12 Jul 2021 15:56:16 +0100
+
 glib2.0 (2.64.6-1~ubuntu20.04.3) focal-security; urgency=medium
 
   * SECURITY UPDATE: incorrect g_file_replace() symlink handling
diff -Nru glib2.0-2.64.6/debian/patches/gvdb-builder-Initialise-some-memory-to-zero-in-the-bloom-.patch glib2.0-2.64.6/debian/patches/gvdb-builder-Initialise-some-memory-to-zero-in-the-bloom-.patch
--- glib2.0-2.64.6/debian/patches/gvdb-builder-Initialise-some-memory-to-zero-in-the-bloom-.patch	1970-01-01 00:00:00.000000000 +0000
+++ glib2.0-2.64.6/debian/patches/gvdb-builder-Initialise-some-memory-to-zero-in-the-bloom-.patch	2021-07-12 14:56:16.000000000 +0000
@@ -0,0 +1,36 @@
+From: Philip Withnall <withnall@endlessm.com>
+Date: Wed, 18 Mar 2020 09:15:59 +0000
+Subject: gvdb-builder: Initialise some memory to zero in the bloom filter
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 8bit
+
+Until a bloom filter is implemented, we need to ensure that all the
+memory returned by `file_builder_allocate()` is initialised, since it’s
+not initialised at allocation time.
+
+Signed-off-by: Philip Withnall <withnall@endlessm.com>
+
+Fixes: #2
+
+Bug: https://gitlab.gnome.org/GNOME/gvdb/-/issues/2
+Bug-Ubuntu: https://bugs.launchpad.net/bugs/1930359
+Origin: backport, https://github.com/GNOME/glib/commit/ea64c739239faea463f3cb9154a12cc4532ba525
+Last-Update: 2021-07-12
+---
+ gio/gvdb/gvdb-builder.c | 2 ++
+ 1 file changed, 2 insertions(+)
+
+diff --git a/gio/gvdb/gvdb-builder.c b/gio/gvdb/gvdb-builder.c
+index 2383e60..aa29d22 100644
+--- a/gio/gvdb/gvdb-builder.c
++++ b/gio/gvdb/gvdb-builder.c
+@@ -339,6 +339,8 @@ file_builder_allocate_for_hash (FileBuilder            *fb,
+ #undef chunk
+ 
+   memset (*bloom_filter, 0, n_bloom_words * sizeof (guint32_le));
++  memset (*hash_buckets, 0, n_buckets * sizeof (guint32_le));
++  memset (*hash_items, 0, n_items * sizeof (struct gvdb_hash_item));
+ 
+   /* NOTE - the code to actually fill in the bloom filter here is missing.
+    * Patches welcome! 
diff -Nru glib2.0-2.64.6/debian/patches/series glib2.0-2.64.6/debian/patches/series
--- glib2.0-2.64.6/debian/patches/series	2021-03-12 16:38:28.000000000 +0000
+++ glib2.0-2.64.6/debian/patches/series	2021-07-12 14:56:16.000000000 +0000
@@ -40,3 +40,4 @@
 CVE-2021-28153-3.patch
 CVE-2021-28153-4.patch
 CVE-2021-28153-5.patch
+gvdb-builder-Initialise-some-memory-to-zero-in-the-bloom-.patch