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CVE-2026-53964

Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes)

7.2 HighFix available

Document Merge Service is a document template merge service providing an API to manage templates and merge them with given data. Prior to version 9.1.0, 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. This issue has been patched in version 9.1.0.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
High
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

0.49%Unchanged since Oct 2, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.2

Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes)

Document Merge Service is a document template merge service providing an API to manage templates and merge them with given data. Prior to version 9.1.0, 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. This issue has been patched in version 9.1.0.

Record
CVE-2026-53964
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1336
Updated
2026-11-02
EUVDEUVD-2026-91047 7.2

Document Merge Service is a document template merge service providing an API to manage templates and merge them with given data. Prior to version 9.1.0, 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. This issue has been patched in version 9.1.0.

Record
EUVD-2026-91047
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-w47q-945m-q9pc 7.2

Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes)

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

Record
GHSA-w47q-945m-q9pc
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1336
Updated
2026-11-02
NVD 7.2

Document Merge Service is a document template merge service providing an API to manage templates and merge them with given data. Prior to version 9.1.0, 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. This issue has been patched in version 9.1.0.

Record
CVE-2026-53964
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1336
Updated
2026-11-02
OSV 7.2

Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes)

Document Merge Service is a document template merge service providing an API to manage templates and merge them with given data. Prior to version 9.1.0, 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. This issue has been patched in version 9.1.0.

Record
CVE-2026-53964
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1336
Updated
2026-11-02
OSVGHSA-w47q-945m-q9pc 7.2

Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes)

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

Record
GHSA-w47q-945m-q9pc
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-1336
Updated
2026-11-02
OSVPYSEC-2026-3830 7.2

Document Merge Service vulnerable to RCE via SSTI (xlsx tempaltes)

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

Record
PYSEC-2026-3830
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
document-merge-service
PyPI
 before 9.1.0
9.1.0
document-merge-service
PyPI
 before 9.1.0, plus listed versions
5.2.05.2.16.0.06.1.06.1.1
Show 27 moreShow less
6.1.26.2.06.2.16.2.26.3.06.3.16.4.06.4.16.4.26.4.36.4.46.4.56.4.66.5.06.5.16.5.26.6.06.6.17.0.07.0.17.0.27.1.08.0.08.0.28.0.38.1.09.0.0
9.1.0

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-53964 is a high vulnerability (CVSS 7.2) in Adfinis Document-merge-service, published August 19, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.49%, the 42nd percentile. Fixed in document-merge-service 9.1.0.

References

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