{"id":"CVE-2026-106118","aliases":["EUVD-2026-93770","GHSA-v76p-62qx-wwq2"],"status":"published","title":"ImageSharp: Tiled fax TIFF: tile buffer sized by TileWidth but fax decompressor writes scanlines of ImageWidth — heap OOB write","description":"ImageSharp is a 2D graphics library. From 3.0.0 until 4.1.1, tiled TIFF decoding allocates a destination buffer using TileWidth but TiffDecompressorsFactory.Create constructs T4, T6, and Modified Huffman decompressors using the full frame width. TiffDecoderCore.DecodeTilesChunky can therefore direct frame-width fax scanlines into a tile-width buffer when TileWidth is smaller than ImageWidth. The mismatch causes attacker-controlled out-of-bounds writes, heap corruption, and process termination even with legal per-row run codes. This tiled-path vulnerability is distinct from oversized CCITT runs in strip decoding. This issue is fixed in version 4.1.1.","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":0.00595,"percentile":0.48957,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-787"],"published":"2026-10-06T17:59:02Z","modified":"2026-10-28T02:31:14Z","fixes":[{"ecosystem":"NuGet","package":"SixLabors.ImageSharp","fixed_in":["3.2.0","4.1.1"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"NuGet","package":"SixLabors.ImageSharp","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.0.0"},{"fixed":"3.2.0"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"SixLabors.ImageSharp","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.0.0"},{"fixed":"4.1.1"}]}]},{"source":"osv","ecosystem":"NuGet","package":"SixLabors.ImageSharp","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.0.0"},{"fixed":"3.2.0"}]}],"versions":["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":"4.1.1"}]}],"versions":["4.0.0","4.1.0"]}],"products":[{"vendor":"sixlabors","product":"imagesharp"}],"references":[{"url":"https://github.com/SixLabors/ImageSharp/security/advisories/GHSA-v76p-62qx-wwq2","tags":["x_refsource_CONFIRM","advisory","web"]},{"url":"https://github.com/SixLabors/ImageSharp/pull/3176","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/SixLabors/ImageSharp/commit/9ee7d1dd5b62d8c9f16cc755e76828386bc2191f","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/SixLabors/ImageSharp/releases/tag/v4.1.1","tags":["x_refsource_MISC","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-106118","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-v76p-62qx-wwq2"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/106xxx/CVE-2026-106118.json","tags":["advisory"]},{"url":"https://github.com/SixLabors/ImageSharp","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-106118","title":"ImageSharp: Tiled fax TIFF: tile buffer sized by TileWidth but fax decompressor writes scanlines of ImageWidth — heap OOB write","description":"ImageSharp is a 2D graphics library. From 3.0.0 until 4.1.1, tiled TIFF decoding allocates a destination buffer using TileWidth but TiffDecompressorsFactory.Create constructs T4, T6, and Modified Huffman decompressors using the full frame width. TiffDecoderCore.DecodeTilesChunky can therefore direct frame-width fax scanlines into a tile-width buffer when TileWidth is smaller than ImageWidth. The mismatch causes attacker-controlled out-of-bounds writes, heap corruption, and process termination even with legal per-row run codes. This tiled-path vulnerability is distinct from oversized CCITT runs in strip decoding. This issue is fixed in version 4.1.1.","status":"published","published":"2026-10-06T17:59:02.778Z","modified":"2026-10-06T19:29:39.226Z","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":"2026-11-02T14:20:04.156238Z"}],"euvd":[{"id":"EUVD-2026-93770","description":"ImageSharp is a 2D graphics library. From 3.0.0 until 4.1.1, tiled TIFF decoding allocates a destination buffer using TileWidth but TiffDecompressorsFactory.Create constructs T4, T6, and Modified Huffman decompressors using the full frame width. TiffDecoderCore.DecodeTilesChunky can therefore direct frame-width fax scanlines into a tile-width buffer when TileWidth is smaller than ImageWidth. The mismatch causes attacker-controlled out-of-bounds writes, heap corruption, and process termination even with legal per-row run codes. This tiled-path vulnerability is distinct from oversized CCITT runs in strip decoding. This issue is fixed in version 4.1.1.","status":"published","published":"2026-10-06T17:59:02Z","modified":"2026-10-06T19:29:39Z","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":"2026-11-02T17:27:36.701921Z"}],"ghsa":[{"id":"GHSA-v76p-62qx-wwq2","title":"ImageSharp: Tiled fax TIFF: tile buffer sized by TileWidth but fax decompressor writes scanlines of ImageWidth — heap OOB write","description":"## Summary\n\nWhen decoding a tiled TIFF with fax compression (T4/T6/MH), `DecodeTilesChunky` allocates each tile buffer from **TileWidth** (`ceil(TileWidth*bpp/8)*TileLength` bytes) but constructs the fax decompressor with **frame.Width**: `TiffDecompressorsFactory` ignores the `isTiled/tileWidth/tileHeight` parameters entirely. The T4/T6/MH decompressors treat the full image width as the scanline length and advance (and really write, via read-modify-write bit ops) `frame.Width` bits per row, with no bounds check against the tile buffer. The very first tile therefore writes linearly out of bounds — about `ImageWidth/8` bytes per row × TileLength rows into a `TileWidth`-sized buffer. With ImageWidth=4,000,000, TileWidth=16, TileLength=16 this writes ~2 MB past a 32-byte buffer and kills the process deterministically; a T6 all-white variant advances the bit offset by \u003e512 MB silently, showing an alarm-free heap-corruption window for the same defect. A crafted file fully controls the OOB length per tile and works with perfectly legal per-row run codes (no overlong runs needed).\n\nVerified at commit `5cd4d0d26a82a9549f297a237aea9cf665bddff8` (main; latest release v4.1.0, the supported major).\n\n## Details\n\nRoot cause: a size mismatch between tile buffer allocation and decompressor width, because the factory drops the tile parameters.\n\n- Allocation: [TiffDecoderCore.cs#L792-L794](https://github.com/SixLabors/ImageSharp/blob/5cd4d0d26a82a9549f297a237aea9cf665bddff8/src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs#L792-L794) — `bytesPerTileRow = RoundUpToMultipleOfEight(tileWidth*bitsPerPixel)`; tile buffer = `bytesPerTileRow*tileLength` bytes (32 bytes in the PoC)\n- Mismatch: [TiffDecoderCore.cs#L797](https://github.com/SixLabors/ImageSharp/blob/5cd4d0d26a82a9549f297a237aea9cf665bddff8/src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs#L797) — `CreateDecompressor\u003cTPixel\u003e(frame.Width, ..., isTiled: true, tileWidth, tileLength)` passes the full frame width\n- Factory drops tile params: [TiffDecompressorsFactory.cs#L56-L64](https://github.com/SixLabors/ImageSharp/blob/5cd4d0d26a82a9549f297a237aea9cf665bddff8/src/ImageSharp/Formats/Tiff/Compression/TiffDecompressorsFactory.cs#L56-L64) — T4/T6/MH decompressors receive only `width` (= frame.Width); `isTiled/tileWidth/tileHeight` ignored\n- OOB write sink: [T4TiffCompression.cs#L69-L119](https://github.com/SixLabors/ImageSharp/blob/5cd4d0d26a82a9549f297a237aea9cf665bddff8/src/ImageSharp/Formats/Tiff/Compression/Decompressors/T4TiffCompression.cs#L69-L119), `T6TiffCompression.cs#L76-L108` — per-row advance of `this.width` bits via `BitWriterUtils.WriteBits` with no buffer-length check ([BitWriterUtils.cs#L51](https://github.com/SixLabors/ImageSharp/blob/5cd4d0d26a82a9549f297a237aea9cf665bddff8/src/ImageSharp/Formats/Tiff/Compression/BitWriterUtils.cs#L51)); note `TiffDecoderCore.cs:829-831` later reads the buffer in `bytesPerTileRow` strides, confirming the protocol expects tile-width rows\n\nAttack surface: `Image.Load(stream)` on an attacker-supplied tiled TIFF (`TiffDecoderCore.DecodeImageWithTiles` → `DecodeTilesChunky`). Default configuration; only requirement is a standard tiled TIFF header (TileWidth=16, TileLength=16) + Compression=3 (T4; T6 also constructible).\n\n**Suggested remediation:**\n1. Short-term: when `isTiled`, construct the T4/T6/MH decompressor with `tileWidth` (not frame width), or clip row writes to the caller-provided buffer length.\n2. Root fix: bound the write side of `BitWriterUtils` (pass remaining bits), and validate every fax row advance against buffer capacity on both tiled and strip paths.\n3. Regression tests: Compression=2/3/4 × tiled with TileWidth \u003c ImageWidth, including a T6 black-pixel row (forces real `WriteBit`).\n\n## PoC\n\nFull PoC posted as the first comment below: `Program.cs` (driver), `poc-tiled-t4.tif` (crafted file, ~9.8 KB, base64 inline), README.\n\n1. Build a small console project referencing `src/ImageSharp/ImageSharp.csproj` and run it against the crafted file (or call `Image.Load` on it from any host).\n2. Observed with ImageWidth=4,000,000, TileWidth=16, TileLength=16, T4 with 400 makeup codes + EOL per row:\n\n   ```\n   tile payload 9642 bytes; rows write ~2,048,000 bytes into a 32-byte buffer\n   Fatal error. System.AccessViolationException: Attempted to read or write protected memory.\n      at SixLabors.ImageSharp.Formats.Tiff.Compression.BitWriterUtils.WriteBits(Span`1\u003cByte\u003e, IntPtr, IntPtr, Byte)\n      at ...T4TiffCompression.WritePixelRun(...)\n      at ...T4TiffCompression.Decompress(...)\n   Aborted (core dumped); exit=134\n   ```\n\n3. Controls: the same file with Compression=None decodes normally (container is fine); a T6 all-white-rows variant advances \u003e512 MB of bit offset without a real write (silent corruption window) before tripping on a directory-level TileOffsets count check.\n\n## Impact\n\n- **What it is:** out-of-bounds write (CWE-787). For any service decoding untrusted tiled TIFFs: remote, default-configuration, deterministic process crash (DoS), plus a heap OOB write whose per-tile length and row width are attacker-tunable — a potential code-execution surface. This is a vulnerability in the library itself, in scope of your SECURITY.md.\n- **Who is impacted:** applications decoding untrusted TIFF with SixLabors.ImageSharp at the current major (verified on main past v4.1.0); tiled + fax-compressed files are the trigger, which ordinary TIFF writers can produce.\n\n---\n\n---\n\nReported by **Kimi Security Team** (bug-report@moonshot.ai).","status":"published","published":"2026-10-07T16:18:57Z","modified":"2026-10-26T16:04:12Z","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-2026-106118","description":"ImageSharp is a 2D graphics library. From 3.0.0 until 4.1.1, tiled TIFF decoding allocates a destination buffer using TileWidth but TiffDecompressorsFactory.Create constructs T4, T6, and Modified Huffman decompressors using the full frame width. TiffDecoderCore.DecodeTilesChunky can therefore direct frame-width fax scanlines into a tile-width buffer when TileWidth is smaller than ImageWidth. The mismatch causes attacker-controlled out-of-bounds writes, heap corruption, and process termination even with legal per-row run codes. This tiled-path vulnerability is distinct from oversized CCITT runs in strip decoding. This issue is fixed in version 4.1.1.","status":"published","published":"2026-10-06T19:17:42.64Z","modified":"2026-10-06T20:17:17.703Z","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-2026-106118","title":"ImageSharp: Tiled fax TIFF: tile buffer sized by TileWidth but fax decompressor writes scanlines of ImageWidth — heap OOB write","description":"ImageSharp is a 2D graphics library. From 3.0.0 until 4.1.1, tiled TIFF decoding allocates a destination buffer using TileWidth but TiffDecompressorsFactory.Create constructs T4, T6, and Modified Huffman decompressors using the full frame width. TiffDecoderCore.DecodeTilesChunky can therefore direct frame-width fax scanlines into a tile-width buffer when TileWidth is smaller than ImageWidth. The mismatch causes attacker-controlled out-of-bounds writes, heap corruption, and process termination even with legal per-row run codes. This tiled-path vulnerability is distinct from oversized CCITT runs in strip decoding. This issue is fixed in version 4.1.1.","status":"published","published":"2026-10-06T17:59:02.778Z","modified":"2026-10-28T02:31:14.807341531Z","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-v76p-62qx-wwq2","title":"ImageSharp: Tiled fax TIFF: tile buffer sized by TileWidth but fax decompressor writes scanlines of ImageWidth — heap OOB write","description":"## Summary\n\nWhen decoding a tiled TIFF with fax compression (T4/T6/MH), `DecodeTilesChunky` allocates each tile buffer from **TileWidth** (`ceil(TileWidth*bpp/8)*TileLength` bytes) but constructs the fax decompressor with **frame.Width**: `TiffDecompressorsFactory` ignores the `isTiled/tileWidth/tileHeight` parameters entirely. The T4/T6/MH decompressors treat the full image width as the scanline length and advance (and really write, via read-modify-write bit ops) `frame.Width` bits per row, with no bounds check against the tile buffer. The very first tile therefore writes linearly out of bounds — about `ImageWidth/8` bytes per row × TileLength rows into a `TileWidth`-sized buffer. With ImageWidth=4,000,000, TileWidth=16, TileLength=16 this writes ~2 MB past a 32-byte buffer and kills the process deterministically; a T6 all-white variant advances the bit offset by \u003e512 MB silently, showing an alarm-free heap-corruption window for the same defect. A crafted file fully controls the OOB length per tile and works with perfectly legal per-row run codes (no overlong runs needed).\n\nVerified at commit `5cd4d0d26a82a9549f297a237aea9cf665bddff8` (main; latest release v4.1.0, the supported major).\n\n## Details\n\nRoot cause: a size mismatch between tile buffer allocation and decompressor width, because the factory drops the tile parameters.\n\n- Allocation: [TiffDecoderCore.cs#L792-L794](https://github.com/SixLabors/ImageSharp/blob/5cd4d0d26a82a9549f297a237aea9cf665bddff8/src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs#L792-L794) — `bytesPerTileRow = RoundUpToMultipleOfEight(tileWidth*bitsPerPixel)`; tile buffer = `bytesPerTileRow*tileLength` bytes (32 bytes in the PoC)\n- Mismatch: [TiffDecoderCore.cs#L797](https://github.com/SixLabors/ImageSharp/blob/5cd4d0d26a82a9549f297a237aea9cf665bddff8/src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs#L797) — `CreateDecompressor\u003cTPixel\u003e(frame.Width, ..., isTiled: true, tileWidth, tileLength)` passes the full frame width\n- Factory drops tile params: [TiffDecompressorsFactory.cs#L56-L64](https://github.com/SixLabors/ImageSharp/blob/5cd4d0d26a82a9549f297a237aea9cf665bddff8/src/ImageSharp/Formats/Tiff/Compression/TiffDecompressorsFactory.cs#L56-L64) — T4/T6/MH decompressors receive only `width` (= frame.Width); `isTiled/tileWidth/tileHeight` ignored\n- OOB write sink: [T4TiffCompression.cs#L69-L119](https://github.com/SixLabors/ImageSharp/blob/5cd4d0d26a82a9549f297a237aea9cf665bddff8/src/ImageSharp/Formats/Tiff/Compression/Decompressors/T4TiffCompression.cs#L69-L119), `T6TiffCompression.cs#L76-L108` — per-row advance of `this.width` bits via `BitWriterUtils.WriteBits` with no buffer-length check ([BitWriterUtils.cs#L51](https://github.com/SixLabors/ImageSharp/blob/5cd4d0d26a82a9549f297a237aea9cf665bddff8/src/ImageSharp/Formats/Tiff/Compression/BitWriterUtils.cs#L51)); note `TiffDecoderCore.cs:829-831` later reads the buffer in `bytesPerTileRow` strides, confirming the protocol expects tile-width rows\n\nAttack surface: `Image.Load(stream)` on an attacker-supplied tiled TIFF (`TiffDecoderCore.DecodeImageWithTiles` → `DecodeTilesChunky`). Default configuration; only requirement is a standard tiled TIFF header (TileWidth=16, TileLength=16) + Compression=3 (T4; T6 also constructible).\n\n**Suggested remediation:**\n1. Short-term: when `isTiled`, construct the T4/T6/MH decompressor with `tileWidth` (not frame width), or clip row writes to the caller-provided buffer length.\n2. Root fix: bound the write side of `BitWriterUtils` (pass remaining bits), and validate every fax row advance against buffer capacity on both tiled and strip paths.\n3. Regression tests: Compression=2/3/4 × tiled with TileWidth \u003c ImageWidth, including a T6 black-pixel row (forces real `WriteBit`).\n\n## PoC\n\nFull PoC posted as the first comment below: `Program.cs` (driver), `poc-tiled-t4.tif` (crafted file, ~9.8 KB, base64 inline), README.\n\n1. Build a small console project referencing `src/ImageSharp/ImageSharp.csproj` and run it against the crafted file (or call `Image.Load` on it from any host).\n2. Observed with ImageWidth=4,000,000, TileWidth=16, TileLength=16, T4 with 400 makeup codes + EOL per row:\n\n   ```\n   tile payload 9642 bytes; rows write ~2,048,000 bytes into a 32-byte buffer\n   Fatal error. System.AccessViolationException: Attempted to read or write protected memory.\n      at SixLabors.ImageSharp.Formats.Tiff.Compression.BitWriterUtils.WriteBits(Span`1\u003cByte\u003e, IntPtr, IntPtr, Byte)\n      at ...T4TiffCompression.WritePixelRun(...)\n      at ...T4TiffCompression.Decompress(...)\n   Aborted (core dumped); exit=134\n   ```\n\n3. Controls: the same file with Compression=None decodes normally (container is fine); a T6 all-white-rows variant advances \u003e512 MB of bit offset without a real write (silent corruption window) before tripping on a directory-level TileOffsets count check.\n\n## Impact\n\n- **What it is:** out-of-bounds write (CWE-787). For any service decoding untrusted tiled TIFFs: remote, default-configuration, deterministic process crash (DoS), plus a heap OOB write whose per-tile length and row width are attacker-tunable — a potential code-execution surface. This is a vulnerability in the library itself, in scope of your SECURITY.md.\n- **Who is impacted:** applications decoding untrusted TIFF with SixLabors.ImageSharp at the current major (verified on main past v4.1.0); tiled + fax-compressed files are the trigger, which ordinary TIFF writers can produce.\n\n---\n\n---\n\nReported by **Kimi Security Team** (bug-report@moonshot.ai).","status":"published","published":"2026-10-07T16:18:57Z","modified":"2026-10-26T16:15:54.080946183Z","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":"2026-11-02T15:46:56.981655Z"}]}}