🛡️ CVE-2021-21703 — libphp

🟠 CVSS 8.0 — High ✅ No Known Exploit OSV
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

PHP-FPM memory access in root process leading to privilege escalation

In PHP versions 7.3.x up to and including 7.3.31, 7.4.x below 7.4.25 and 8.0.x below 8.0.12, when running PHP FPM SAPI with main FPM daemon process running as root and child worker processes running as lower-privileged users, it is possible for the child processes to access memory shared with the main process and write to it, modifying it in a way that would cause the root process to conduct invalid memory reads and writes, which can be used to escalate privileges from local unprivileged user to the root user.

Affected software

CVE-2021-21703 is recorded against 3 packages.

  • libphp
  • php
  • php-min

Timeline and source

Published on 11 August 2025. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

www.openwall.com (Web)
bugs.php.net (Web)
lists.debian.org (Web)
lists.fedoraproject.org (Web)
lists.fedoraproject.org (Web)
lists.fedoraproject.org (Web)
nvd.nist.gov (Web)
security.gentoo.org (Web)
security.netapp.com (Web)
www.debian.org (Web)
www.debian.org (Web)
www.oracle.com (Web)
www.oracle.com (Web)

CVE-2021-21703 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector N/A
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2025-08-11
Updated 2026-08-12
Modified 2025-08-11
Fix URL N/A

Affected Packages

Software From version Fixed in
libphp — —
php — —
php-min — —

References

Similar Threats

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