CVE-2021-21707: Debian Linux

Medium severity, CVSS 5.3. EPSS: 26% chance of exploitation in the next 30 days.

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 Debian Linux: version 10.0 only; version 11.0 only
• Netapp Clustered Data Ontap: affected versions not specified
• PHP PHP: from 7.3.0, before 7.3.33 (fixed in 7.3.33); from 7.4.0, before 7.4.26 (fixed in 7.4.26); from 8.0.0, before 8.0.13 (fixed in 8.0.13)
• Tenable Tenable.sc: before 5.21.0 (fixed in 5.21.0)

Published 2021-11-29. Last modified 2026-06-17.