diff --git a/package-updates/package-updates-lib.pl b/package-updates/package-updates-lib.pl
index df4609635..978916e2b 100644
--- a/package-updates/package-updates-lib.pl
+++ b/package-updates/package-updates-lib.pl
@@ -11,6 +11,7 @@ use Data::Dumper;
 
 $available_cache_file = "$module_config_directory/available.cache";
 $current_cache_file = "$module_config_directory/current.cache";
+$updates_cache_file = "$module_config_directory/updates.cache";
 $cron_cmd = "$module_config_directory/update.pl";
 
 $yum_cache_file = "$module_config_directory/yumcache";
@@ -246,6 +247,37 @@ if (defined(&software::update_system_available)) {
 return ( );
 }
 
+sub supports_updates_available
+{
+return defined(&software::update_system_updates);
+}
+
+# updates_available(no-cache)
+# Returns an array of hash refs of package updates available, according to
+# the update system, with caching.
+sub updates_available
+{
+my ($nocache) = @_;
+if (!defined(@updates_available_cache)) {
+	if ($nocache || &cache_expired($updates_cache_file)) {
+		# Get from original source
+		@updates_available_cache = &software::update_system_updates();
+		foreach my $a (@updates_available_cache) {
+			$a->{'update'} = $a->{'name'};
+			$a->{'system'} = $software::update_system;
+			}
+		&write_cache_file($updates_cache_file,
+				  \@updates_available_cache);
+		}
+	else {
+		# Use on-disk cache
+		@updates_available_cache =
+			&read_cache_file($updates_cache_file);
+		}
+	}
+return @updates_available_cache;
+}
+
 # package_install(package, [system])
 # Install some package, either from an update system or from Webmin. Returns
 # a list of updated package names.
@@ -314,28 +346,52 @@ sub list_possible_updates
 my ($nocache) = @_;
 my @rv;
 my @current = &list_current($nocache);
-my @avail = &list_available($nocache == 1);
-my %availmap;
-foreach my $a (@avail) {
-	my $oa = $availmap{$a->{'name'},$a->{'system'}};
-	if (!$oa || &compare_versions($a, $oa) > 0) {
-		$availmap{$a->{'name'},$a->{'system'}} = $a;
+if (&supports_updates_available()) {
+	my %currentmap;
+	foreach my $c (@current) {
+		$currentmap{$c->{'name'},$c->{'system'}} ||= $c;
 		}
-	}
-foreach my $c (sort { $a->{'name'} cmp $b->{'name'} } @current) {
-	# Work out the status
-	my $a = $availmap{$c->{'name'},$c->{'system'}};
-	if ($a->{'version'} && &compare_versions($a, $c) > 0) {
-		# A regular update is available
+	foreach my $a (&updates_available($nocache == 1)) {
+		my $c = $currentmap{$a->{'name'},$a->{'system'}};
+		next if (!$c);
+		next if ($a->{'version'} eq $c->{'version'});
 		push(@rv, { 'name' => $a->{'name'},
 			    'update' => $a->{'update'},
 			    'system' => $a->{'system'},
 			    'version' => $a->{'version'},
 			    'oldversion' => $c->{'version'},
 			    'epoch' => $a->{'epoch'},
+			    'oldepoch' => $c->{'epoch'},
 			    'security' => $a->{'security'},
-			    'desc' => $c->{'desc'} || $a->{'desc'},
-			    'severity' => 0 });
+			    'desc' => $c->{'desc'} || $a->{'desc'} });
+		}
+	}
+else {
+	# Compute from current and available list
+	my @avail = &list_available($nocache == 1);
+	my %availmap;
+	foreach my $a (@avail) {
+		my $oa = $availmap{$a->{'name'},$a->{'system'}};
+		if (!$oa || &compare_versions($a, $oa) > 0) {
+			$availmap{$a->{'name'},$a->{'system'}} = $a;
+			}
+		}
+	foreach my $c (sort { $a->{'name'} cmp $b->{'name'} } @current) {
+		# Work out the status
+		my $a = $availmap{$c->{'name'},$c->{'system'}};
+		if ($a->{'version'} && &compare_versions($a, $c) > 0) {
+			# A regular update is available
+			push(@rv, { 'name' => $a->{'name'},
+				    'update' => $a->{'update'},
+				    'system' => $a->{'system'},
+				    'version' => $a->{'version'},
+				    'oldversion' => $c->{'version'},
+				    'epoch' => $a->{'epoch'},
+				    'oldepoch' => $c->{'epoch'},
+				    'security' => $a->{'security'},
+				    'desc' => $c->{'desc'} || $a->{'desc'},
+				    'severity' => 0 });
+			}
 		}
 	}
 return @rv;
diff --git a/software/CHANGELOG b/software/CHANGELOG
index dbd185c1b..270d1f958 100644
--- a/software/CHANGELOG
+++ b/software/CHANGELOG
@@ -30,3 +30,6 @@ The selected package and update systems are now checked when the module is opene
 ---- Changes since 1.470 ----
 On Solaris, added support for the pkgutil command from Blastwave for installing packages, which replaces the old pkg-get.
 On Solaris, package versions are now shown in the package list and tree.
+---- Changes since 1.500 ----
+Fixed several bugs related to YUM available package updates.
+Added the update_system_updates function to more efficiently find available packages for YUM and APT.
diff --git a/software/yum-lib.pl b/software/yum-lib.pl
index dd15dbc69..f0bc12b24 100755
--- a/software/yum-lib.pl
+++ b/software/yum-lib.pl
@@ -196,21 +196,53 @@ while(<PKG>) {
 		}
 	}
 close(PKG);
+&set_yum_security_field(\%done);
+return @rv;
+}
 
-# Also run list-sec to find out which are security updates
-&open_execute_command(PKG, "yum list-sec", 1, 1);
+# set_yum_security_field(&package-hash)
+# Set security field on packages which are security updates
+sub set_yum_security_field
+{
+local ($done) = @_;
+&open_execute_command(PKG, "yum list-sec 2>/dev/null", 1, 1);
 while(<PKG>) {
 	s/\r|\n//g;
 	if (/^\S+\s+security\s+(\S+?)\-([0-9]\S+)\.([^\.]+)$/) {
 		local ($name, $ver) = ($1, $2);
-		if ($done{$name}) {
-			$done{$name}->{'source'} = 'security';
-			$done{$name}->{'security'} = 1;
+		if ($done->{$name}) {
+			$done->{$name}->{'source'} = 'security';
+			$done->{$name}->{'security'} = 1;
 			}
 		}
 	}
 close(PKG);
+}
 
+# update_system_updates()
+# Returns a list of package updates available from yum
+sub update_system_updates
+{
+local @rv;
+local %done;
+&open_execute_command(PKG, "yum check-update 2>/dev/null", 1, 1);
+while(<PKG>) {
+        s/\r|\n//g;
+	if (/^(\S+)\.([^\.]+)\s+(\S+)\s+(\S+)/) {
+		local $pkg = { 'name' => $1,
+			       'arch' => $2,
+			       'version' => $3,
+			       'source' => $4 };
+		$pkg->{'version'} = $1;
+		if ($pkg->{'version'} =~ s/^(\S+)://) {
+			$pkg->{'epoch'} = $1;
+			}
+		$done{$pkg} = $pkg->{'name'};
+		push(@rv, $pkg);
+		}
+	}
+close(PKG);
+&set_yum_security_field(\%done);
 return @rv;
 }