diff --git a/libcontainer/system/proc.go b/libcontainer/system/proc.go
index d0407cfe4..8f0a68afd 100644
--- a/libcontainer/system/proc.go
+++ b/libcontainer/system/proc.go
@@ -19,6 +19,8 @@ const ( // Only values for Linux 3.14 and later are listed here
 	Stopped     State = 'T'
 	TracingStop State = 't'
 	Zombie      State = 'Z'
+	Parked      State = 'P'
+	Idle        State = 'I'
 )
 
 // String forms of the state from proc(5)'s documentation for
@@ -39,6 +41,10 @@ func (s State) String() string {
 		return "tracing stop"
 	case Zombie:
 		return "zombie"
+	case Parked:
+		return "parked"
+	case Idle:
+		return "idle" // kernel thread
 	default:
 		return fmt.Sprintf("unknown (%c)", s)
 	}
@@ -48,9 +54,6 @@ func (s State) String() string {
 // described in proc(5) with names based on the /proc/[pid]/status
 // fields.
 type Stat_t struct {
-	// PID is the process ID.
-	PID uint
-
 	// Name is the command run by the process.
 	Name string
 
@@ -72,32 +75,53 @@ func Stat(pid int) (stat Stat_t, err error) {
 }
 
 func parseStat(data string) (stat Stat_t, err error) {
-	// From proc(5), field 2 could contain space and is inside `(` and `)`.
-	// The following is an example:
+	// Example:
 	// 89653 (gunicorn: maste) S 89630 89653 89653 0 -1 4194560 29689 28896 0 3 146 32 76 19 20 0 1 0 2971844 52965376 3920 18446744073709551615 1 1 0 0 0 0 0 16781312 137447943 0 0 0 17 1 0 0 0 0 0 0 0 0 0 0 0 0 0
-	i := strings.LastIndex(data, ")")
-	if i <= 2 || i >= len(data)-1 {
-		return stat, fmt.Errorf("invalid stat data: %q", data)
+	// The fields are space-separated, see full description in proc(5).
+	//
+	// We are only interested in:
+	//  * field 2: process name. It is the only field enclosed into
+	//    parenthesis, as it can contain spaces (and parenthesis) inside.
+	//  * field 3: process state, a single character (%c)
+	//  * field 22: process start time, a long unsigned integer (%llu).
+
+	// 1. Look for the first '(' and the last ')' first, what's in between is Name.
+	//    We expect at least 20 fields and a space after the last one.
+
+	const minAfterName = 20*2 + 1 // the min field is '0 '.
+
+	first := strings.IndexByte(data, '(')
+	if first < 0 || first+minAfterName >= len(data) {
+		return stat, fmt.Errorf("invalid stat data (no comm or too short): %q", data)
 	}
 
-	parts := strings.SplitN(data[:i], "(", 2)
-	if len(parts) != 2 {
-		return stat, fmt.Errorf("invalid stat data: %q", data)
+	last := strings.LastIndexByte(data, ')')
+	if last <= first || last+minAfterName >= len(data) {
+		return stat, fmt.Errorf("invalid stat data (no comm or too short): %q", data)
 	}
 
-	stat.Name = parts[1]
-	_, err = fmt.Sscanf(parts[0], "%d", &stat.PID)
+	stat.Name = data[first+1 : last]
+
+	// 2. Remove fields 1 and 2 and a space after. State is right after.
+	data = data[last+2:]
+	stat.State = State(data[0])
+
+	// 3. StartTime is field 22, data is at field 3 now, so we need to skip 19 spaces.
+	skipSpaces := 22 - 3
+	for first = 0; skipSpaces > 0 && first < len(data); first++ {
+		if data[first] == ' ' {
+			skipSpaces--
+		}
+	}
+	// Now first points to StartTime; look for space right after.
+	i := strings.IndexByte(data[first:], ' ')
+	if i < 0 {
+		return stat, fmt.Errorf("invalid stat data (too short): %q", data)
+	}
+	stat.StartTime, err = strconv.ParseUint(data[first:first+i], 10, 64)
 	if err != nil {
-		return stat, err
+		return stat, fmt.Errorf("invalid stat data (bad start time): %w", err)
 	}
 
-	// parts indexes should be offset by 3 from the field number given
-	// proc(5), because parts is zero-indexed and we've removed fields
-	// one (PID) and two (Name) in the paren-split.
-	parts = strings.Split(data[i+2:], " ")
-	var state int
-	fmt.Sscanf(parts[3-3], "%c", &state) //nolint:staticcheck // "3-3" is more readable in this context.
-	stat.State = State(state)
-	fmt.Sscanf(parts[22-3], "%d", &stat.StartTime)
 	return stat, nil
 }
diff --git a/libcontainer/system/proc_test.go b/libcontainer/system/proc_test.go
index 7e1acc5bc..949d8403e 100644
--- a/libcontainer/system/proc_test.go
+++ b/libcontainer/system/proc_test.go
@@ -1,45 +1,180 @@
 package system
 
-import "testing"
+import (
+	"errors"
+	"math/bits"
+	"os"
+	"reflect"
+	"strconv"
+	"testing"
+)
 
-func TestParseStartTime(t *testing.T) {
-	data := map[string]Stat_t{
-		"4902 (gunicorn: maste) S 4885 4902 4902 0 -1 4194560 29683 29929 61 83 78 16 96 17 20 0 1 0 9126532 52965376 1903 18446744073709551615 4194304 7461796 140733928751520 140733928698072 139816984959091 0 0 16781312 137447943 1 0 0 17 3 0 0 9 0 0 9559488 10071156 33050624 140733928758775 140733928758945 140733928758945 140733928759264 0": {
-			PID:       4902,
-			Name:      "gunicorn: maste",
-			State:     'S',
-			StartTime: 9126532,
-		},
-		"9534 (cat) R 9323 9534 9323 34828 9534 4194304 95 0 0 0 0 0 0 0 20 0 1 0 9214966 7626752 168 18446744073709551615 4194304 4240332 140732237651568 140732237650920 140570710391216 0 0 0 0 0 0 0 17 1 0 0 0 0 0 6340112 6341364 21553152 140732237653865 140732237653885 140732237653885 140732237656047 0": {
-			PID:       9534,
-			Name:      "cat",
-			State:     'R',
-			StartTime: 9214966,
-		},
+var procdata = map[string]Stat_t{
+	"4902 (gunicorn: maste) S 4885 4902 4902 0 -1 4194560 29683 29929 61 83 78 16 96 17 20 0 1 0 9126532 52965376 1903 18446744073709551615 4194304 7461796 140733928751520 140733928698072 139816984959091 0 0 16781312 137447943 1 0 0 17 3 0 0 9 0 0 9559488 10071156 33050624 140733928758775 140733928758945 140733928758945 140733928759264 0": {
+		Name:      "gunicorn: maste",
+		State:     'S',
+		StartTime: 9126532,
+	},
+	"9534 (cat) R 9323 9534 9323 34828 9534 4194304 95 0 0 0 0 0 0 0 20 0 1 0 9214966 7626752 168 18446744073709551615 4194304 4240332 140732237651568 140732237650920 140570710391216 0 0 0 0 0 0 0 17 1 0 0 0 0 0 6340112 6341364 21553152 140732237653865 140732237653885 140732237653885 140732237656047 0": {
+		Name:      "cat",
+		State:     'R',
+		StartTime: 9214966,
+	},
+	"12345 ((ugly )pr()cess() R 9323 9534 9323 34828 9534 4194304 95 0 0 0 0 0 0 0 20 0 1 0 9214966 7626752 168 18446744073709551615 4194304 4240332 140732237651568 140732237650920 140570710391216 0 0 0 0 0 0 0 17 1 0 0 0 0 0 6340112 6341364 21553152 140732237653865 140732237653885 140732237653885 140732237656047 0": {
+		Name:      "(ugly )pr()cess(",
+		State:     'R',
+		StartTime: 9214966,
+	},
+	"24767 (irq/44-mei_me) S 2 0 0 0 -1 2129984 0 0 0 0 0 0 0 0 -51 0 1 0 8722075 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 0 0 0 17 1 50 1 0 0 0 0 0 0 0 0 0 0 0": {
+		Name:      "irq/44-mei_me",
+		State:     'S',
+		StartTime: 8722075,
+	},
+	"0 () I 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0": {
+		Name:      "",
+		State:     'I',
+		StartTime: 0,
+	},
+	// Not entirely correct, but minimally viable input (StartTime and a space after).
+	"1 (woo hoo) S 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ": {
+		Name:      "woo hoo",
+		State:     'S',
+		StartTime: 4,
+	},
+}
 
-		"24767 (irq/44-mei_me) S 2 0 0 0 -1 2129984 0 0 0 0 0 0 0 0 -51 0 1 0 8722075 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 0 0 0 17 1 50 1 0 0 0 0 0 0 0 0 0 0 0": {
-			PID:       24767,
-			Name:      "irq/44-mei_me",
-			State:     'S',
-			StartTime: 8722075,
-		},
-	}
-	for line, expected := range data {
+func TestParseStat(t *testing.T) {
+	for line, exp := range procdata {
 		st, err := parseStat(line)
 		if err != nil {
-			t.Fatal(err)
-		}
-		if st.PID != expected.PID {
-			t.Fatalf("expected PID %q but received %q", expected.PID, st.PID)
-		}
-		if st.State != expected.State {
-			t.Fatalf("expected state %q but received %q", expected.State, st.State)
-		}
-		if st.Name != expected.Name {
-			t.Fatalf("expected name %q but received %q", expected.Name, st.Name)
-		}
-		if st.StartTime != expected.StartTime {
-			t.Fatalf("expected start time %q but received %q", expected.StartTime, st.StartTime)
+			t.Errorf("input %q, unexpected error %v", line, err)
+		} else if !reflect.DeepEqual(st, exp) {
+			t.Errorf("input %q, expected %+v, got %+v", line, exp, st)
 		}
 	}
 }
+
+func TestParseStatBadInput(t *testing.T) {
+	cases := []struct {
+		desc, input string
+	}{
+		{
+			"no (",
+			"123 ) S 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0",
+		},
+		{
+			"no )",
+			"123 ( S 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0",
+		},
+		{
+			") at end",
+			"123 (cmd) S 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0)",
+		},
+		{
+			"misplaced ()",
+			"123 )one( S 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0",
+		},
+		{
+			"misplaced empty ()",
+			"123 )( S 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0",
+		},
+		{
+			"empty line",
+			"",
+		},
+		{
+			"short line",
+			"123 (cmd) S 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0",
+		},
+		{
+			"short line (no space after stime)",
+			"123 (cmd) S 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 42",
+		},
+		{
+			"bad stime",
+			"123 (cmd) S 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1 ",
+		},
+		{
+			"bad stime 2", // would be valid if not -1
+			"123 (cmd) S                   -1 ",
+		},
+		{
+			"a tad short",
+			"1234 (cmd) ",
+		},
+		{
+			"bad stime",
+			"123 (cmd) S 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1",
+		},
+	}
+	for _, c := range cases {
+		st, err := parseStat(c.input)
+		if err == nil {
+			t.Errorf("case %q, expected error, got nil, %+v", c.desc, st)
+		}
+	}
+}
+
+func BenchmarkParseStat(b *testing.B) {
+	var (
+		st, exp Stat_t
+		line    string
+		err     error
+	)
+
+	for i := 0; i != b.N; i++ {
+		for line, exp = range procdata {
+			st, err = parseStat(line)
+		}
+	}
+	if err != nil {
+		b.Fatal(err)
+	}
+	if !reflect.DeepEqual(st, exp) {
+		b.Fatal("wrong result")
+	}
+}
+
+func BenchmarkParseRealStat(b *testing.B) {
+	var (
+		st    Stat_t
+		err   error
+		total int
+	)
+	b.StopTimer()
+	fd, err := os.Open("/proc")
+	if err != nil {
+		b.Fatal(err)
+	}
+	defer fd.Close()
+
+	for i := 0; i != b.N; i++ {
+		count := 0
+		if _, err := fd.Seek(0, 0); err != nil {
+			b.Fatal(err)
+		}
+		names, err := fd.Readdirnames(-1)
+		if err != nil {
+			b.Fatal(err)
+		}
+		for _, n := range names {
+			pid, err := strconv.ParseUint(n, 10, bits.UintSize)
+			if err != nil {
+				continue
+			}
+			b.StartTimer()
+			st, err = Stat(int(pid))
+			b.StopTimer()
+			if err != nil {
+				// Ignore a process that just finished.
+				if errors.Is(err, os.ErrNotExist) {
+					continue
+				}
+				b.Fatal(err)
+			}
+			count++
+		}
+		total += count
+	}
+	b.Logf("N: %d, parsed %d pids, last stat: %+v, err: %v", b.N, total, st, err)
+}