Backport: V3 - Throw explicit InvalidImageContentException when BMP BPP is invalid.

.github/workflows/build-and-test.yml

@@ -25,7 +25,7 @@ jobs:
             sdk-preview: true
             runtime: -x64
             codecov: false
-          - os: macos-13 # macos-latest runs on arm64 runners where libgdiplus is unavailable
+          - os: macos-26
             framework: net7.0
             sdk: 7.0.x
             sdk-preview: true
@@ -48,7 +48,7 @@ jobs:
             sdk: 6.0.x
             runtime: -x64
             codecov: false
-          - os: macos-13 # macos-latest runs on arm64 runners where libgdiplus is unavailable
+          - os: macos-26 
             framework: net6.0
             sdk: 6.0.x
             runtime: -x64
@@ -69,8 +69,20 @@ jobs:
       - name: Install libgdi+, which is required for tests running on ubuntu
         if: ${{ contains(matrix.options.os, 'ubuntu') }}
         run: |
-            sudo apt-get update
-            sudo apt-get -y install libgdiplus libgif-dev libglib2.0-dev libcairo2-dev libtiff-dev libexif-dev
+          sudo apt-get update
+          sudo apt-get -y install libgdiplus libgif-dev libglib2.0-dev libcairo2-dev libtiff-dev libexif-dev
+
+      - name: Install libgdi+, which is required for tests running on macos
+        if: ${{ contains(matrix.options.os, 'macos-26') }}
+        run: |
+          brew update
+          brew install mono-libgdiplus
+          # Create symlinks to make libgdiplus discoverable
+          sudo mkdir -p /usr/local/lib
+          sudo ln -sf $(brew --prefix)/lib/libgdiplus.dylib /usr/local/lib/libgdiplus.dylib
+          # Verify installation
+          ls -la $(brew --prefix)/lib/libgdiplus* || echo "libgdiplus not found in brew prefix"
+          ls -la /usr/local/lib/libgdiplus* || echo "libgdiplus not found in /usr/local/lib"
 
       - name: Git Config
         shell: bash

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -126,7 +126,10 @@ protected override Image<TPixel> Decode<TPixel>(BufferedReadStream stream, Cance
             switch (this.infoHeader.Compression)
             {
                 case BmpCompression.RGB:
-                    if (this.infoHeader.BitsPerPixel == 32)
+
+                    ushort bitsPerPixel = this.infoHeader.BitsPerPixel;
+
+                    if (bitsPerPixel == 32)
                     {
                         if (this.bmpMetadata.InfoHeaderType == BmpInfoHeaderType.WinVersion3)
                         {
@@ -137,26 +140,30 @@ protected override Image<TPixel> Decode<TPixel>(BufferedReadStream stream, Cance
                             this.ReadRgb32Fast(stream, pixels, this.infoHeader.Width, this.infoHeader.Height, inverted);
                         }
                     }
-                    else if (this.infoHeader.BitsPerPixel == 24)
+                    else if (bitsPerPixel == 24)
                     {
                         this.ReadRgb24(stream, pixels, this.infoHeader.Width, this.infoHeader.Height, inverted);
                     }
-                    else if (this.infoHeader.BitsPerPixel == 16)
+                    else if (bitsPerPixel == 16)
                     {
                         this.ReadRgb16(stream, pixels, this.infoHeader.Width, this.infoHeader.Height, inverted);
                     }
-                    else if (this.infoHeader.BitsPerPixel <= 8)
+                    else if (bitsPerPixel is > 0 and <= 8)
                     {
                         this.ReadRgbPalette(
                             stream,
                             pixels,
                             palette,
                             this.infoHeader.Width,
                             this.infoHeader.Height,
-                            this.infoHeader.BitsPerPixel,
+                            bitsPerPixel,
                             bytesPerColorMapEntry,
                             inverted);
                     }
+                    else
+                    {
+                        BmpThrowHelper.ThrowInvalidImageContentException($"Invalid bits per pixel: {bitsPerPixel}");
+                    }
 
                     break;
 

tests/ImageSharp.Tests/Formats/Bmp/BmpDecoderTests.cs

@@ -570,4 +570,27 @@ public void BmpDecoder_ThrowsException_Issue2696<TPixel>(TestImageProvider<TPixe
             });
         Assert.IsType<InvalidMemoryOperationException>(ex.InnerException);
     }
+
+    [Fact]
+    public void BmpDecoder_ThrowsException_Issue3067()
+    {
+        // Construct minimal BMP with bitsPerPixel = 0
+        byte[] bmp = new byte[54];
+        bmp[0] = (byte)'B';
+        bmp[1] = (byte)'M';
+        BitConverter.GetBytes(54).CopyTo(bmp, 2);
+        BitConverter.GetBytes(54).CopyTo(bmp, 10);
+        BitConverter.GetBytes(40).CopyTo(bmp, 14);
+        BitConverter.GetBytes(1).CopyTo(bmp, 18);
+        BitConverter.GetBytes(1).CopyTo(bmp, 22);
+        BitConverter.GetBytes((short)1).CopyTo(bmp, 26);
+        BitConverter.GetBytes((short)0).CopyTo(bmp, 28);  // bitsPerPixel = 0
+
+        using MemoryStream stream = new(bmp);
+
+        InvalidImageContentException ex = Assert.Throws<InvalidImageContentException>(() =>
+        {
+            using Image image = BmpDecoder.Instance.Decode(DecoderOptions.Default, stream);
+        });
+    }
 }