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PYSEC-2026-3830

Vulnerability from pysec - Published: 2026-09-10 09:44 - Updated: 2026-09-10 11:02
VLAI
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
Impacted products
Name purl
document-merge-service pkg:pypi/document-merge-service
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "document-merge-service",
        "purl": "pkg:pypi/document-merge-service"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "9.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.2.0",
        "5.2.1",
        "6.0.0",
        "6.1.0",
        "6.1.1",
        "6.1.2",
        "6.2.0",
        "6.2.1",
        "6.2.2",
        "6.3.0",
        "6.3.1",
        "6.4.0",
        "6.4.1",
        "6.4.2",
        "6.4.3",
        "6.4.4",
        "6.4.5",
        "6.4.6",
        "6.5.0",
        "6.5.1",
        "6.5.2",
        "6.6.0",
        "6.6.1",
        "7.0.0",
        "7.0.1",
        "7.0.2",
        "7.1.0",
        "8.0.0",
        "8.0.2",
        "8.0.3",
        "8.1.0",
        "9.0.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-53964",
    "GHSA-w47q-945m-q9pc"
  ],
  "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": "PYSEC-2026-3830",
  "modified": "2026-09-10T11:02:05.469619Z",
  "published": "2026-09-10T09:44:51.968052Z",
  "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"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/document-merge-service"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-w47q-945m-q9pc"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53964"
    }
  ],
  "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.

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • 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.


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