Out-of-Bounds Write in SixLabors.ImageSharp (CVE-2026-106115)
Summary
Out-of-bounds write in SixLabors.ImageSharp (CVE-2026-106115). Risk of unauthorized operations or information disclosure. Exploitable via TiffEncoder. Mitigation: upgrade to 4.1.2 or later.
Original description
The description as published by the source.
Summary
The TIFF CCITT Group 4 (T6) encoder writes beyond its logical compressed-data buffer when encoding a 1-bit image. A valid 1×1 Group 4 TIFF decoded and re-encoded with the default TiffEncoder terminates the process with an unhandled exception.
Affected package and versions
- Package:
SixLabors.ImageSharp(NuGet) - Affected range:
>= 2.1.0, <= 4.1.1 - Commit
0815358f9202a78bc7f3b83e19282dc3654b500fcorresponds to release v4.1.1.
The T6 compressor was introduced by commit 3c9eb470a07a15012c2a29ad84090dcc804a7975, first released in v2.1.0, with the same Width * rowsPerStrip allocation and unchecked code writes. The 1×1 exploit terminates published v2.1.0 and v4.1.1; its uncompressed control succeeds. Source history shows no capacity fix through v4.1.1.
Details
TiffCcittCompressor.Initialize allocates Width * rowsPerStrip bytes. A 1×1 strip therefore receives one byte.
After encoding the row, T6BitCompressor.CompressStrip appends two 12-bit EOFB codes. [WriteCode](https://github.com/SixLabors/ImageSharp/blob/0815358f9202a78bc7f3b83e19282dc3654b500f/src/ImageSharp/Formats/Tiff/Compression/Compres…
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-2026-106115 has been found in SixLabors.ImageSharp.
Attackers can target a specific entry point like TiffEncoder over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade SixLabors.ImageSharp to 4.1.2 or later.
If unsure, ask your IT team or search "SixLabors.ImageSharp CVE-2026-106115" on the vendor's site.
CVE-2026-106115 (SixLabors.ImageSharp) — CWE-787 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: TiffEncoder / SixLabors.ImageSharp / TiffCcittCompressor.Initialize / T6BitCompressor.CompressStrip
Patched: 4.1.2 — 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 SixLabors.ImageSharp. Attackers reach the vulnerable code path via TiffEncoder without authentication.
Check the vendor advisory for the affected versions of SixLabors.ImageSharp. Attack surface: TiffEncoder / SixLabors.ImageSharp / TiffCcittCompressor.Initialize / T6BitCompressor.CompressStrip.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 4.1.2.
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 'SixLabors.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
-
1Identify exposure identify
grep -r 'SixLabors.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
SixLabors.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 SixLabors.ImageSharp to 4.1.2ステージング環境で 4.1.2 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。