Out-of-Bounds Write in ImageSharp (CVE-2026-106118)
Summary
Out-of-bounds write in ImageSharp (CVE-2026-106118). Risk of unauthorized operations or information disclosure. Exploitable via DecodeTilesChunky. Mitigation: upgrade to 4.1.1 or later.
Original description
The description as published by the source.
Summary
When 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 >512 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).
Verified at commit 5cd4d0d26a82a9549f297a237aea9cf665bddff8 (main; latest release v4.1.0, the supported major).
Details
Root cause: a size mismatch between tile buffer allocation and decompressor width, because the factory drops the tile parameters.
- Allocation: [TiffDecoderCore.cs#L792-L794](https://github.com/SixLabors/ImageSharp/blob/5cd4d0d26a82a9549f297a237aea9cf665bddff8/src/ImageSharp/Form…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-106118 has been found in ImageSharp.
Attackers can target a specific entry point like DecodeTilesChunky over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade ImageSharp to 4.1.1 or later.
If unsure, ask your IT team or search "ImageSharp CVE-2026-106118" on the vendor's site.
CVE-2026-106118 (ImageSharp) — CWE-787 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: DecodeTilesChunky / TiffDecompressorsFactory / frame.Width / TileWidth
Patched: 4.1.1 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Out-of-bounds write (CWE-787) exists in ImageSharp. Attackers reach the vulnerable code path via DecodeTilesChunky without authentication.
Check the vendor advisory for the affected versions of ImageSharp. Attack surface: DecodeTilesChunky / TiffDecompressorsFactory / frame.Width / TileWidth.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 4.1.1.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'ImageSharp' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'ImageSharp' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
ImageSharpを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade ImageSharp to 4.1.1ステージング環境で 4.1.1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com