ImageSharp is a 2D graphics library. From 1.0.0-beta0001 until 4.1.2, ICC CLUT parsing calculates allocation sizes from attacker-declared channel and grid dimensions before confirming that the profile contains the declared values. IccDataReader.ReadClutF32 can request a large float array, and earlier public IccProfile.Entries parsing paths can allocate a large jagged representation, from a short truncated profile. In version 4, automatic image conversion reaches the parser when DecoderOptions.ColorProfileHandling is Convert; the default Preserve mode avoids that conversion path. The demonstrated impact is memory pressure and input-validation failure, not unhandled process termination. This issue is fixed in version 4.1.2.

Affected: NuGet: SixLabors.ImageSharp

### Summary

A malformed embedded ICC profile can make ImageSharp allocate memory from attacker-controlled CLUT channel and grid dimensions before verifying that the declared CLUT values are present.

In published v1 through v3 packages, the public lazy ICC parser allocates approximately 115 MB from the 200-byte test profile before rejecting the truncated tag. In published v4 packages, decoding with ICC conversion enabled requests an 860,934,420-byte managed float array from the same profile.

### Affected package and versions

- Package: `SixLabors.ImageSharp` (NuGet) - Affected range: `>= 1.0.0-beta0001, <= 4.1.1` - Commit `0815358f9202a78bc7f3b83e19282dc3654b500f` corresponds to release **v4.1.1**.

The parser defect is present from the first published NuGet prerelease, `1.0.0-beta0001`, through the latest published release, 4.1.1. The automatic `Image.Load` conversion path used by the main PoC exists in `>= 4.0.0, <= 4.1.1`; earlier versions expose the same parser defect through the public `IccProfile.Entries` accessor. ### Details

The reproduced profile has an `A2B0` multi-process-elements (`mpet`) tag with a `clut` element declaring 15 input channels, 15 output channels, and three grid points per input channel. [`ReadClutF32`](https://github.com/SixLabors/ImageSharp/blob/0815358f9202a78bc7f3b83e19282dc3654b500f/src/ImageSharp/Metadata/Profiles/ICC/DataReader/IccDataReader.Lut.cs#L139-L162) computes `3^15 * 15` and allocates that many floats before reading any CLUT val…