Vulnerability in document-merge-service (CVE-2026-53964)
Summary
Vulnerability in document-merge-service (CVE-2026-53964). Successful exploitation can lead to full system takeover. Exploitable via xltpl. Mitigation: upgrade to 9.1.0 or later.
Original description
The description as published by the source.
Impact
A remote code execution (RCE) via server-side template injection (SSTI) allows for user supplied code to be executed in the server's context where it is executed as the document-merge-server user with the UID 901 thus giving an attacker considerable control over the container. The vulnerability is limited to XLSX templates, were the xltpl library uses a npn-sandboxed Jinja environment for the processing of the template.
Patches
It has been patched in v9.1.0
Workarounds
Disable the upload/usage of XLSX templates.
References
Are there any links users can visit to find out more?
https://book.hacktricks.xyz/pentesting-web/ssti-server-side-template-injection/jinja2-ssti
Source: GitHub Security Advisories (Global) 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-2026-53964 has been found in document-merge-service.
Attackers can target a specific entry point like xltpl over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 7.2/10.
What to do: upgrade document-merge-service to 9.1.0 or later.
If unsure, ask your IT team or search "document-merge-service CVE-2026-53964" on the vendor's site.
CVE-2026-53964 (document-merge-service) — CWE-1336 / CVSS v3 7.2
Attack vector: remote (network-reachable) / no user interaction
Attack surface: xltpl
Patched: 9.1.0 — apply immediately
Workaround: Disable the upload/usage of XLSX templates.
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.
A vulnerability (CWE-1336) exists in document-merge-service. Attackers reach the vulnerable code path via xltpl.
Check the vendor advisory for the affected versions of document-merge-service. Attack surface: xltpl.
Severity: High (CVSS 7.2/10). Successful exploitation can lead to full system takeover.
Update to 9.1.0.
Workaround: Disable the upload/usage of XLSX templates.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'document-merge-service' . 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 'document-merge-service' . | 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
document-merge-serviceを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
Disable the upload/usage of XLSX templates.パッチが適用されるまでの応急処置として、Disable the upload/usage of XLSX templates. を実施。回避策の副作用 (機能低下) を確認した上で。
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3Apply patch patch
Upgrade document-merge-service to 9.1.0ステージング環境で 9.1.0 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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4Post-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。