diff --git a/session/bootstrap.go b/session/bootstrap.go
index e2ef6f854e594..d380d91676772 100644
--- a/session/bootstrap.go
+++ b/session/bootstrap.go
@@ -794,16 +794,21 @@ const (
 	version111 = 111
 	// version112 modifies the view tidb_mdl_view
 	version112 = 112
-	// version113 modifies the following global variables default value:
+	// ...
+	// [version113, version119] is the version range reserved for patches of 6.5.x
+	// ...
+	// version113 sets tidb_server_memory_limit to "80%"
+	version113 = 113
+	// version120 modifies the following global variables default value:
 	// - foreign_key_checks: off -> on
 	// - tidb_enable_foreign_key: off -> on
 	// - tidb_store_batch_size: 0 -> 4
-	version113 = 113
+	version120 = 120
 )
 
 // currentBootstrapVersion is defined as a variable, so we can modify its value for testing.
 // please make sure this is the largest version
-var currentBootstrapVersion int64 = version113
+var currentBootstrapVersion int64 = version120
 
 // DDL owner key's expired time is ManagerSessionTTL seconds, we should wait the time and give more time to have a chance to finish it.
 var internalSQLTimeout = owner.ManagerSessionTTL + 15
@@ -924,6 +929,7 @@ var (
 		upgradeToVer111,
 		upgradeToVer112,
 		upgradeToVer113,
+		upgradeToVer120,
 	}
 )
 
@@ -2295,7 +2301,14 @@ func upgradeToVer113(s Session, ver int64) {
 	if ver >= version113 {
 		return
 	}
+	mustExecute(s, "UPDATE HIGH_PRIORITY %n.%n set VARIABLE_VALUE = %? where VARIABLE_NAME = %? and VARIABLE_VALUE = %?;",
+		mysql.SystemDB, mysql.GlobalVariablesTable, variable.DefTiDBServerMemoryLimit, variable.TiDBServerMemoryLimit, "0")
+}
 
+func upgradeToVer120(s Session, ver int64) {
+	if ver >= version120 {
+		return
+	}
 	mustExecute(s, "REPLACE HIGH_PRIORITY INTO %n.%n VALUES (%?, %?);", mysql.SystemDB, mysql.GlobalVariablesTable, variable.ForeignKeyChecks, variable.On)
 	mustExecute(s, "REPLACE HIGH_PRIORITY INTO %n.%n VALUES (%?, %?);", mysql.SystemDB, mysql.GlobalVariablesTable, variable.TiDBEnableForeignKey, variable.On)
 	mustExecute(s, "REPLACE HIGH_PRIORITY INTO %n.%n VALUES (%?, %?);", mysql.SystemDB, mysql.GlobalVariablesTable, variable.TiDBEnableHistoricalStats, variable.On)
diff --git a/session/bootstrap_test.go b/session/bootstrap_test.go
index 832ba478dfed3..4c07d31d7bc49 100644
--- a/session/bootstrap_test.go
+++ b/session/bootstrap_test.go
@@ -1418,6 +1418,112 @@ func TestTiDBGCAwareUpgradeFrom630To650(t *testing.T) {
 	require.Equal(t, "0", row.GetString(1))
 }
 
+func TestTiDBServerMemoryLimitUpgradeTo651_1(t *testing.T) {
+	ctx := context.Background()
+	store, _ := createStoreAndBootstrap(t)
+	defer func() { require.NoError(t, store.Close()) }()
+
+	// upgrade from 6.5.0 to 6.5.1+.
+	ver112 := version112
+	seV112 := createSessionAndSetID(t, store)
+	txn, err := store.Begin()
+	require.NoError(t, err)
+	m := meta.NewMeta(txn)
+	err = m.FinishBootstrap(int64(ver112))
+	require.NoError(t, err)
+	err = txn.Commit(context.Background())
+	require.NoError(t, err)
+	mustExec(t, seV112, fmt.Sprintf("update mysql.tidb set variable_value=%d where variable_name='tidb_server_version'", ver112))
+	mustExec(t, seV112, fmt.Sprintf("update mysql.GLOBAL_VARIABLES set variable_value='%s' where variable_name='%s'", "0", variable.TiDBServerMemoryLimit))
+	mustExec(t, seV112, "commit")
+	unsetStoreBootstrapped(store.UUID())
+	ver, err := getBootstrapVersion(seV112)
+	require.NoError(t, err)
+	require.Equal(t, int64(ver112), ver)
+
+	// We are now in 6.5.0, tidb_server_memory_limit is 0.
+	res := mustExecToRecodeSet(t, seV112, fmt.Sprintf("select * from mysql.GLOBAL_VARIABLES where variable_name='%s'", variable.TiDBServerMemoryLimit))
+	chk := res.NewChunk(nil)
+	err = res.Next(ctx, chk)
+	require.NoError(t, err)
+	require.Equal(t, 1, chk.NumRows())
+	row := chk.GetRow(0)
+	require.Equal(t, 2, row.Len())
+	require.Equal(t, "0", row.GetString(1))
+
+	// Upgrade to 6.5.1+.
+	domCurVer, err := BootstrapSession(store)
+	require.NoError(t, err)
+	defer domCurVer.Close()
+	seCurVer := createSessionAndSetID(t, store)
+	ver, err = getBootstrapVersion(seCurVer)
+	require.NoError(t, err)
+	require.Equal(t, currentBootstrapVersion, ver)
+
+	// We are now in 6.5.1+.
+	res = mustExecToRecodeSet(t, seCurVer, fmt.Sprintf("select * from mysql.GLOBAL_VARIABLES where variable_name='%s'", variable.TiDBServerMemoryLimit))
+	chk = res.NewChunk(nil)
+	err = res.Next(ctx, chk)
+	require.NoError(t, err)
+	require.Equal(t, 1, chk.NumRows())
+	row = chk.GetRow(0)
+	require.Equal(t, 2, row.Len())
+	require.Equal(t, variable.DefTiDBServerMemoryLimit, row.GetString(1))
+}
+
+func TestTiDBServerMemoryLimitUpgradeTo651_2(t *testing.T) {
+	ctx := context.Background()
+	store, _ := createStoreAndBootstrap(t)
+	defer func() { require.NoError(t, store.Close()) }()
+
+	// upgrade from 6.5.0 to 6.5.1+.
+	ver112 := version112
+	seV112 := createSessionAndSetID(t, store)
+	txn, err := store.Begin()
+	require.NoError(t, err)
+	m := meta.NewMeta(txn)
+	err = m.FinishBootstrap(int64(ver112))
+	require.NoError(t, err)
+	err = txn.Commit(context.Background())
+	require.NoError(t, err)
+	mustExec(t, seV112, fmt.Sprintf("update mysql.tidb set variable_value=%d where variable_name='tidb_server_version'", ver112))
+	mustExec(t, seV112, fmt.Sprintf("update mysql.GLOBAL_VARIABLES set variable_value='%s' where variable_name='%s'", "70%", variable.TiDBServerMemoryLimit))
+	mustExec(t, seV112, "commit")
+	unsetStoreBootstrapped(store.UUID())
+	ver, err := getBootstrapVersion(seV112)
+	require.NoError(t, err)
+	require.Equal(t, int64(ver112), ver)
+
+	// We are now in 6.5.0, tidb_server_memory_limit is "70%".
+	res := mustExecToRecodeSet(t, seV112, fmt.Sprintf("select * from mysql.GLOBAL_VARIABLES where variable_name='%s'", variable.TiDBServerMemoryLimit))
+	chk := res.NewChunk(nil)
+	err = res.Next(ctx, chk)
+	require.NoError(t, err)
+	require.Equal(t, 1, chk.NumRows())
+	row := chk.GetRow(0)
+	require.Equal(t, 2, row.Len())
+	require.Equal(t, "70%", row.GetString(1))
+
+	// Upgrade to 6.5.1+.
+	domCurVer, err := BootstrapSession(store)
+	require.NoError(t, err)
+	defer domCurVer.Close()
+	seCurVer := createSessionAndSetID(t, store)
+	ver, err = getBootstrapVersion(seCurVer)
+	require.NoError(t, err)
+	require.Equal(t, currentBootstrapVersion, ver)
+
+	// We are now in 6.5.1+.
+	res = mustExecToRecodeSet(t, seCurVer, fmt.Sprintf("select * from mysql.GLOBAL_VARIABLES where variable_name='%s'", variable.TiDBServerMemoryLimit))
+	chk = res.NewChunk(nil)
+	err = res.Next(ctx, chk)
+	require.NoError(t, err)
+	require.Equal(t, 1, chk.NumRows())
+	row = chk.GetRow(0)
+	require.Equal(t, 2, row.Len())
+	require.Equal(t, "70%", row.GetString(1))
+}
+
 func TestTiDBGlobalVariablesDefaultValueUpgradeFrom630To660(t *testing.T) {
 	ctx := context.Background()
 	store, _ := createStoreAndBootstrap(t)