diff --git a/Tests/images/custom_gimp_palette.gpl b/Tests/images/custom_gimp_palette.gpl
index 08ea7002849..ced2f243176 100644
--- a/Tests/images/custom_gimp_palette.gpl
+++ b/Tests/images/custom_gimp_palette.gpl
@@ -1,12 +1,12 @@
 GIMP Palette
 Name: custompalette
 Columns: 4
-#
-  0   0   0     Index 3
- 65  38  30     Index 4
-103  62  49     Index 6
- 79  73  72     Index 7
-114 101  97     Index 8
-208 127 100     Index 9
-151 144 142     Index 10
-221 207 199     Index 11
+# Original written by David Wetz in https://stackoverflow.com/questions/815836/im-creating-a-program-that-generates-a-palette-from-a-true-color-image-need-hel/815855#815855
+  0   0   0     Index 0
+ 65  38  30     Index 1
+103  62  49     Index 2
+ 79  73  72     Index 3
+114 101  97     Index 4
+208 127 100     Index 5
+151 144 142     Index 6
+221 207 199     Index 7
diff --git a/Tests/test_file_gimppalette.py b/Tests/test_file_gimppalette.py
index caec9cf2115..e6587ff7c0b 100644
--- a/Tests/test_file_gimppalette.py
+++ b/Tests/test_file_gimppalette.py
@@ -20,6 +20,17 @@ def test_sanity():
             GimpPaletteFile(fp)
 
 
+def test_large_file_is_truncated():
+    original_max_file_size = GimpPaletteFile._max_file_size
+    try:
+        GimpPaletteFile._max_file_size = 100
+        with open("Tests/images/custom_gimp_palette.gpl", "rb") as fp:
+            with pytest.warns(UserWarning):
+                GimpPaletteFile(fp)
+    finally:
+        GimpPaletteFile._max_file_size = original_max_file_size
+
+
 def test_get_palette():
     # Arrange
     with open("Tests/images/custom_gimp_palette.gpl", "rb") as fp:
@@ -29,4 +40,17 @@ def test_get_palette():
     palette, mode = palette_file.getpalette()
 
     # Assert
+    expected_palette = []
+    for color in (
+        (0, 0, 0),
+        (65, 38, 30),
+        (103, 62, 49),
+        (79, 73, 72),
+        (114, 101, 97),
+        (208, 127, 100),
+        (151, 144, 142),
+        (221, 207, 199),
+    ):
+        expected_palette += color
+    assert palette == bytes(expected_palette)
     assert mode == "RGB"
diff --git a/src/PIL/GimpPaletteFile.py b/src/PIL/GimpPaletteFile.py
index 2e9cbe58d20..1f7605866ef 100644
--- a/src/PIL/GimpPaletteFile.py
+++ b/src/PIL/GimpPaletteFile.py
@@ -15,8 +15,7 @@
 #
 
 import re
-
-from ._binary import o8
+import warnings
 
 
 class GimpPaletteFile:
@@ -24,35 +23,49 @@ class GimpPaletteFile:
 
     rawmode = "RGB"
 
-    def __init__(self, fp):
+    #: override if reading larger palettes is needed
+    max_colors = 256
+    _max_line_size = 100
+    _max_file_size = 2**20  # 1MB
 
-        self.palette = [o8(i) * 3 for i in range(256)]
+    def __init__(self, fp):
 
         if fp.readline()[:12] != b"GIMP Palette":
             msg = "not a GIMP palette file"
             raise SyntaxError(msg)
 
-        for i in range(256):
+        read = 0
 
-            s = fp.readline()
+        self.palette = []
+        while len(self.palette) < 3 * self.max_colors:
+
+            s = fp.readline(self._max_file_size)
             if not s:
                 break
 
+            read += len(s)
+            if read >= self._max_file_size:
+                warnings.warn(
+                    f"Palette file truncated at {self._max_file_size - len(s)} bytes"
+                )
+                break
+
             # skip fields and comment lines
             if re.match(rb"\w+:|#", s):
                 continue
-            if len(s) > 100:
+            if len(s) > self._max_line_size:
                 msg = "bad palette file"
                 raise SyntaxError(msg)
 
-            v = tuple(map(int, s.split()[:3]))
-            if len(v) != 3:
+            # 4th column is color name and may contain spaces.
+            v = s.split(maxsplit=3)
+            if len(v) < 3:
                 msg = "bad palette entry"
                 raise ValueError(msg)
 
-            self.palette[i] = o8(v[0]) + o8(v[1]) + o8(v[2])
+            self.palette += (int(v[0]), int(v[1]), int(v[2]))
 
-        self.palette = b"".join(self.palette)
+        self.palette = bytes(self.palette)
 
     def getpalette(self):