Validate decoded image dimensions

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -1560,6 +1560,11 @@ internal sealed class BmpDecoderCore : ImageDecoderCore
             this.infoHeader.Height = -this.infoHeader.Height;
         }
 
+        if (this.infoHeader.Width <= 0 || this.infoHeader.Height <= 0)
+        {
+            BmpThrowHelper.ThrowInvalidImageContentException("Width and height must be greater than 0.");
+        }
+
         int bytesPerColorMapEntry = 4;
         int colorMapSizeBytes = -1;
         if (this.infoHeader.ClrUsed == 0)

src/ImageSharp/Formats/Gif/GifDecoderCore.cs

@@ -261,11 +261,6 @@ internal sealed class GifDecoderCore : ImageDecoderCore
             this.currentLocalColorTable?.Dispose();
         }
 
-        if (this.logicalScreenDescriptor.Width == 0 && this.logicalScreenDescriptor.Height == 0)
-        {
-            GifThrowHelper.ThrowNoHeader();
-        }
-
         // Ignoring a malformed ancillary extension must not let identify succeed for a file
         // that never contained any readable image frame data.
         if (previousFrame is null)
@@ -328,6 +323,10 @@ internal sealed class GifDecoderCore : ImageDecoderCore
         }
 
         this.logicalScreenDescriptor = GifLogicalScreenDescriptor.Parse(this.buffer);
+        if (this.logicalScreenDescriptor.Width == 0 || this.logicalScreenDescriptor.Height == 0)
+        {
+            GifThrowHelper.ThrowInvalidImageContentException("Width and height must be greater than 0.");
+        }
     }
 
     /// <summary>

src/ImageSharp/Formats/Tga/TgaDecoderCore.cs

@@ -72,9 +72,9 @@ internal sealed class TgaDecoderCore : ImageDecoderCore
                 TgaThrowHelper.ThrowNotSupportedException($"Unknown tga colormap type {this.fileHeader.ColorMapType} found");
             }
 
-            if (this.fileHeader.Width == 0 || this.fileHeader.Height == 0)
+            if (this.fileHeader.Width <= 0 || this.fileHeader.Height <= 0)
             {
-                throw new UnknownImageFormatException("Width or height cannot be 0");
+                TgaThrowHelper.ThrowInvalidImageContentException("Width and height must be greater than 0.");
             }
 
             Image<TPixel> image = new(this.configuration, this.fileHeader.Width, this.fileHeader.Height, this.metadata);

tests/ImageSharp.Tests/Formats/InvalidImageDimensionsTests.cs

@@ -0,0 +1,18 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Tests.Formats;
+
+public class InvalidImageDimensionsTests
+{
+    [Theory]
+    [InlineData("Qk1GAAAAAAAAADYAAAAoAAAAAgACAAAAAAABABgAAAAAABAAAAATCwAAEwsAAAAAAAAAAAAAAAD/AP8AAAAAAP8A/wAAAA==")]
+    [InlineData("R0lGODdhAgIAAIEAAAD/AP8AAAAA/wAAACwAAAQAAgACAAAIBwADABAQICAAOw==")]
+    [InlineData("AAACAAAAAAAAAAAAAgDCsRgAAgAAAP8A/wD/AAAA//8=")]
+    public void Load_WithNonPositiveDimensions_ThrowsInvalidImageContentException(string encodedData)
+    {
+        byte[] data = Convert.FromBase64String(encodedData);
+
+        Assert.Throws<InvalidImageContentException>(() => Image.Load(data));
+    }
+}