Out-of-Bounds Write in ImageSharp (CVE-2026-106117)
Summary
Out-of-bounds write in ImageSharp (CVE-2026-106117). Risk of unauthorized operations or information disclosure. Exploitable via Unsafe.Add. Mitigation: upgrade to 4.1.1 or later.
Original description
The description as published by the source.
Summary
When decoding a fax-compressed strip TIFF (Compression=3 / Group 3 1D, or Compression=2 / Modified Huffman), the CCITT decompressors write decoded runs through BitWriterUtils.WriteBits/WriteBit/WriteZeroBit, which advance and write bits via Unsafe.Add with read-modify-write semantics — without ever comparing the write position against the target buffer length. The strip buffer is sized ImageWidth × RowsPerStrip (8 bytes in the PoC), but two independent defects let an attacker write tens of millions of bits past it: (a) T4 only increments rowsWritten when an EOL code is read, and one ReadNextRun accumulates unlimited makeup codes (+2560 px per 12-bit code) into a single RunLength that WritePixelRun then writes in one shot; (b) Modified Huffman writes before validating (pixelsWritten > Width is checked at :90-93, after the write at :56-63), so the overflow completes even though an exception is thrown later. One crafted ~90 KB file writes ~19.2 MB linearly past an 8-byte buffer and deterministically kills the process; the write offset and length are fully attacker-controlled (classic heap-corruption primitive on the managed heap).
Verified at commit 5cd4d0d26a82a9549f297a237aea9cf665bddff8 (main; latest release v4.1.0, the supported major). A related tiled-path variant (tile-buffer width mismatch) was reported separately as GHSA-v76p-62qx-wwq2 — this report covers the distinct strip-path root cause.
Details
Root cause: the bit-writing…
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-2026-106117 has been found in ImageSharp.
Attackers can target a specific entry point like Unsafe.Add 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-2026-106117" on the vendor's site.
CVE-2026-106117 (ImageSharp) — CWE-787 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Unsafe.Add / rowsWritten / ReadNextRun / RunLength
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 Unsafe.Add without authentication.
Check the vendor advisory for the affected versions of ImageSharp. Attack surface: Unsafe.Add / rowsWritten / ReadNextRun / RunLength.
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。
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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
- web github.com