SSRF (Server-Side Request Forgery) in github.com/gotenberg/gotenberg/v8 (CVE-2026-42591)
Summary
SSRF in github.com/gotenberg/gotenberg/v8 (CVE-2026-42591). Confidential information can be exposed externally. Exploitable via GET /GOTENBERG_SSRF.
Original description
The description as published by the source.
Summary
The SSRF hardening shipped in v8.31.0 only covers outbound URLs that Gotenberg's Go code handles — Chromium asset fetches, webhook delivery, and download-from. The LibreOffice conversion endpoint (/forms/libreoffice/convert) passes uploaded documents directly to LibreOffice without inspecting their content. LibreOffice then fetches any embedded external URLs on its own, completely bypassing the SSRF filters.
This was verified on v8.31.0 (latest at time of writing) with a crafted DOCX and got 3 outbound HTTP requests from LibreOffice to the canary server used for testing.
Details
When a file is uploaded to /forms/libreoffice/convert, the route in pkg/modules/libreoffice/routes.go reads form parameters and passes the input file directly to libreOffice.Pdf():
err = libreOffice.Pdf(ctx, ctx.Log(), inputPath, outputPaths[i], options)
There's no content inspection happening before the file reaches LibreOffice. The SSRF protection in v8.31.0 (pkg/gotenberg/outbound.go) wraps Go's http.Client with a custom dialer that resolves URLs and rejects non-public IPs — but LibreOffice is a separate process that makes its own HTTP connections via libcurl. The Go-level dial hooks can't intercept that.
OOXML formats like DOCX can embed external image references using TargetMode="External" in relationship files. LibreOffice fetches those URLs during PDF conversion.
Suggested fix: Run LibreOffice with unshare --net to drop all network access fr…
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-2026-42591 has been found in github.com/gotenberg/gotenberg/v8.
Attackers can target a specific entry point like GET /GOTENBERG_SSRF over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.2/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "github.com/gotenberg/gotenberg/v8 CVE-2026-42591" on the vendor's site.
CVE-2026-42591 (github.com/gotenberg/gotenberg/v8) — CWE-918 / CVSS v3 8.2
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: GET /GOTENBERG_SSRF / http.Client
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.
SSRF (CWE-918) exists in github.com/gotenberg/gotenberg/v8. Attackers reach the vulnerable code path via GET /GOTENBERG_SSRF without authentication.
Check the vendor advisory for the affected versions of github.com/gotenberg/gotenberg/v8. Attack surface: GET /GOTENBERG_SSRF / http.Client.
Severity: High (CVSS 8.2/10). Confidential information can be exposed externally.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual GET /GOTENBERG_SSRF requests with malformed payloads or SQL meta-characters. Run grep -r 'github.com/gotenberg/gotenberg/v8' . 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 'github.com/gotenberg/gotenberg/v8' . | 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
github.com/gotenberg/gotenberg/v8を grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'GET /GOTENBERG_SSRF' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
GET /GOTENBERG_SSRFへの異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Post-deployment verification verify
Replay attack against GET /GOTENBERG_SSRF on staging to confirm patch closes the vector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 Step 2 と同じログクエリ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