# CVE-2021-21707

## Summary

- **CVE ID:** CVE-2021-21707
- **Severity:** MEDIUM
- **CVSS Score:** 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N)
- **CWE:** CWE-159
- **Published:** Nov 29, 2021
- **Last Modified:** Mar 13, 2026

## Description

In PHP versions 7.3.x below 7.3.33, 7.4.x below 7.4.26 and 8.0.x below 8.0.13, certain XML parsing functions, like simplexml_load_file(), URL-decode the filename passed to them. If that filename contains URL-encoded NUL character, this may cause the function to interpret this as the end of the filename, thus interpreting the filename differently from what the user intended, which may lead it to reading a different file than intended.

## Affected Products

- PHP Group — PHP (7.3.x)
- PHP Group — PHP (7.4.x)
- PHP Group — PHP (8.0.X)

## References

- [CNA](https://bugs.php.net/bug.php?id=79971)
- [CNA](https://security.netapp.com/advisory/ntap-20211223-0005/)
- [CNA](https://www.debian.org/security/2022/dsa-5082)
- [CNA](https://www.tenable.com/security/tns-2022-09)
- [CNA](https://lists.debian.org/debian-lts-announce/2022/12/msg00030.html)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.56%
- **EPSS Percentile:** 67.9

---
_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._