CVE-2021-21703

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

At a glance

Severity
HIGH 7.8
EPSS
EPSS 1.43 % · percentile 73 (2026-10-27)
State
PUBLISHED
Published
Updated
Assigner
php
NVD status
Modified

Description

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.

Scores

VersionScoreVectorScored by
CVSS 3.1HIGH 7.8CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:Hphp
CVSS 3.1HIGH 7.8CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:HNVD · security@php.net (Secondary)
CVSS 3.1HIGH 7.0CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:HNVD · nvd@nist.gov (Primary)
CVSS 2.0MEDIUM 6.9AV:L/AC:M/Au:N/C:C/I:C/A:CNVD · nvd@nist.gov (Primary)

Weaknesses (CWE)

European references

CERT-FR advisories

Affected configurations (NVD CPE)

Affected products

ProductVersions
PHP Group · PHPaffected 7.3.x ≤ 7.3.31 ; affected 7.4.x < 7.4.25 ; affected 8.0.X < 8.0.12

References

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD