What’s Vulnerable › Vulnerabilities
CVE-2021-21707: Special characters break path parsing in XML functions
- Severity: medium (CVSS 5.3 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 25.3% probability of exploitation in the next 30 days
- Public exploit or detection template: yes
- Published: 2021-11-29 · updated 2026-06-17
- Weakness: CWE-159
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
- Debian Linux: 10.0, 11.0
- Clustered Data ONTAP: all versions
- PHP: from 7.3.0 before 7.3.33; from 7.4.0 before 7.4.26; from 8.0.0 before 8.0.13 — fixed in 7.3.33, 7.4.26, 8.0.13
- Tenable.sc: before 5.21.0 — fixed in 5.21.0
How to fix
Upgrade to a fixed version: PHP 7.3.33, 7.4.26, 8.0.13; Tenable.sc 5.21.0. Check the vendor advisory for mitigations.
References
- https://bugs.php.net/bug.php?id=79971
- https://lists.debian.org/debian-lts-announce/2022/12/msg00030.html
- https://security.netapp.com/advisory/ntap-20211223-0005/
- https://www.debian.org/security/2022/dsa-5082
- https://www.tenable.com/security/tns-2022-09
- https://bugs.php.net/bug.php?id=79971
- https://lists.debian.org/debian-lts-announce/2022/12/msg00030.html
- https://security.netapp.com/advisory/ntap-20211223-0005/
- https://www.debian.org/security/2022/dsa-5082
- https://www.tenable.com/security/tns-2022-09
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