{"id":"PYSEC-2026-3830","summary":"Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes)","details":"### Impact\nA 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. \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","aliases":["CVE-2026-53964","GHSA-w47q-945m-q9pc"],"modified":"2026-09-10T12:15:05.605719783Z","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"}],"affected":[{"package":{"name":"document-merge-service","ecosystem":"PyPI","purl":"pkg:pypi/document-merge-service"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"9.1.0"}]}],"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"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/document-merge-service/PYSEC-2026-3830.yaml"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H"}]}