CVE-2021-39371: XML External Entity Injection in PyWPS
Summary
CVE-2021-39371: XML External Entity Injection in PyWPS. Affects pywps versions < 4.5.0. Fixed in 4.5.0. How to fix ↓
Also tracked for
- pywps · Debian:11
The same CVE-2021-39371 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Background
PyWPS is a Python library that provides an implementation of the Web Processing Service (WPS) standard. It allows users to publish, discover, and execute geospatial processes over the web. PyWPS is widely used in various applications and frameworks for geospatial data processing. However, a vulnerability has been discovered in PyWPS versions prior to 4.5.0 that allows an attacker to perform XML external entity (XXE) injection. This vulnerability can be exploited to view files on the application server filesystem by assigning a path to the entity. OWSLib 0.24.1, a dependency of PyWPS, may also be affected.
Vulnerability Detail
The XML external entity (XXE) injection vulnerability in PyWPS allows an attacker to manipulate XML input and exploit the application's XML parsing functionality. By injecting specially crafted XML entities, an attacker can force the application to access arbitrary files on the server's filesystem. This can lead to unauthorized disclosure of sensitive information, such as configuration files, credentials, or other sensitive data stored on the server. The vulnerability has a CVSS score of 7.5, indicating a high severity level.
How To Fix
Latest published version: 4.8.1 as of 22 Oct 2026
pip install --upgrade "pywps==4.8.1"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
4.5.0
This is the first release that contains the fix.
pip install --upgrade "pywps==4.5.0"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, developers can disable external entity resolution in the XML parser configuration. This can be achieved by modifying the XML parser settings to disallow the resolution of external entities. However, this workaround may impact the functionality of legitimate XML processing within the application. It is recommended to apply this workaround cautiously and prioritize upgrading to the fixed versions of PyWPS and OWSLib.
Conclusion
The XML external entity (XXE) injection vulnerability in PyWPS versions prior to 4.5.0 poses a significant risk to the confidentiality of sensitive information stored on the server's filesystem. It is crucial for users of PyWPS to upgrade to the fixed version and ensure that OWSLib is also updated to address any potential XXE vulnerabilities. Developers should review their XML parsing code and implement proper input validation to prevent XXE attacks. For further assistance and support in remediating this vulnerability, please contact DevNack.com.
See every vulnerability recorded for pywps →
FAQ
PyWPS is a Python library that implements the Web Processing Service (WPS) standard. It allows users to publish, discover, and execute geospatial processes over the web.
XML external entity (XXE) injection is a vulnerability that allows an attacker to manipulate XML input and exploit the application's XML parsing functionality. By injecting specially crafted XML entities, an attacker can force the application to access arbitrary files on the server's filesystem.
The XXE injection vulnerability in PyWPS can lead to unauthorized disclosure of sensitive information stored on the server's filesystem. This includes configuration files, credentials, or other sensitive data that may be accessible to the application.
The CVSS score of this vulnerability is 7.5, indicating a high severity level.
To mitigate this vulnerability, it is recommended to upgrade PyWPS to version 4.5.0 or later and update OWSLib to the latest version. Additionally, developers should review their application's XML parsing code and implement proper input validation and sanitization measures to prevent XXE attacks.
References
Related vulnerabilities
Recent vulnerabilities recorded for pywps.
