diff --git a/src/CalendarVersioning/CalendarVersion.cs b/src/CalendarVersioning/CalendarVersion.cs
index cdf778f..17b9462 100644
--- a/src/CalendarVersioning/CalendarVersion.cs
+++ b/src/CalendarVersioning/CalendarVersion.cs
@@ -30,13 +30,17 @@ public static CalendarVersion Parse(string input, CalendarVersionFormat? format
             if (string.IsNullOrWhiteSpace(input))
                 throw new ArgumentException("Input cannot be null or empty", nameof(input));
 
+            if (input.Length > 256)
+                throw new ArgumentException("Input version string is too long", nameof(input));
 
             int year = 0, month = 0;
             int? day = null, minor = null;
 
-            var parts = input.Split('.');
+            string[] parts;
             if (format == null)
             {
+                parts = input.Split('.', 5);
+
                 // Default parsing: YYYY.MM[.DD[.Minor]]
                 if (parts.Length is < 2 or > 4)
                     throw new FormatException($"Version string '{input}' does not match default format 'YYYY.MM[.DD[.Minor]]'");
@@ -51,7 +55,9 @@ public static CalendarVersion Parse(string input, CalendarVersionFormat? format
 
             // Parsing using the format
             string pattern = format.Pattern;
-            var tokens = pattern.Split('.');
+            var tokens = pattern.Split('.', 10);
+            parts = input.Split('.', tokens.Length + 1);
+
             if (tokens.Length != parts.Length)
                 throw new FormatException($"Version string '{input}' does not match format '{pattern}'");
 
diff --git a/tests/CalendarVersioning.Tests/UnitTests/ParsingTests.cs b/tests/CalendarVersioning.Tests/UnitTests/ParsingTests.cs
index 23173d4..c48b0bf 100644
--- a/tests/CalendarVersioning.Tests/UnitTests/ParsingTests.cs
+++ b/tests/CalendarVersioning.Tests/UnitTests/ParsingTests.cs
@@ -103,5 +103,27 @@ public void Parse_CustomFormat_InvalidYY_ShouldThrowFormatException()
             var format = new CalendarVersionFormat("YY.MM");
             Assert.Throws<FormatException>(() => CalendarVersion.Parse("123.04", format));
         }
+
+        [Fact]
+        public void Parse_TooLongInput_ShouldThrowArgumentException()
+        {
+            string longInput = new string('a', 257);
+            Assert.Throws<ArgumentException>(() => CalendarVersion.Parse(longInput));
+        }
+
+        [Fact]
+        public void Parse_TooManyDots_ShouldThrowFormatException()
+        {
+            string inputWithManyDots = "2025.04.01.1.extra.dots"; // 6 parts
+            Assert.Throws<FormatException>(() => CalendarVersion.Parse(inputWithManyDots));
+        }
+
+        [Fact]
+        public void Parse_CustomFormat_TooManyDots_ShouldThrowFormatException()
+        {
+            var format = new CalendarVersionFormat("YYYY.MM");
+            string inputWithManyDots = "2025.04.01"; // 3 parts for 2 tokens
+            Assert.Throws<FormatException>(() => CalendarVersion.Parse(inputWithManyDots, format));
+        }
     }
 }
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