GHSA-W47Q-945M-Q9PC

Vulnerability from github – Published: 2026-08-19 19:17 – Updated: 2026-08-19 19:17
VLAI
Summary
Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes)
Details

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

Severity
7.2 (High)
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "document-merge-service"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "9.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-53964"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1336"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-19T19:17:19Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Impact\nA remote code execution (RCE) via server-side template injection (SSTI) allows for user supplied code to be executed in the server\u0027s 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. \n\n### Patches\nIt has been patched in [v9.1.0](https://github.com/adfinis/document-merge-service/releases/tag/v9.1.0)\n\n### Workarounds\nDisable the upload/usage of XLSX templates.\n\n### References\nAre there any links users can visit to find out more?\n\nhttps://book.hacktricks.xyz/pentesting-web/ssti-server-side-template-injection/jinja2-ssti",
  "id": "GHSA-w47q-945m-q9pc",
  "modified": "2026-08-19T19:17:19Z",
  "published": "2026-08-19T19:17:19Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/adfinis/document-merge-service/security/advisories/GHSA-w47q-945m-q9pc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/adfinis/document-merge-service"
    },
    {
      "type": "WEB",
      "url": "https://github.com/adfinis/document-merge-service/releases/tag/v9.1.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes)"
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.