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CVE-2021-21703— PHP-FPM memory access in root process leading to privilege escalation

Quick assessment

Affected
PHP Group PHP
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

PHP是一种在服务器端执行的脚本语言。 PHP 存在缓冲区错误漏洞，攻击者可以通过 FPM 绕过 PHP 的访问限制，以读取或更改数据。

CVSS 7.8 · High EPSS 1.43% · P72

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation
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I. Basic Information for CVE-2021-21703

Vulnerability Information
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Vulnerability Title
PHP-FPM memory access in root process leading to privilege escalation
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5
Vulnerability Title
PHP 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
PHP是一种在服务器端执行的脚本语言。 PHP 存在缓冲区错误漏洞，攻击者可以通过 FPM 绕过 PHP 的访问限制，以读取或更改数据。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
PHP Group PHP 7.3.x ~ 7.3.31 -

II. Public POCs for CVE-2021-21703

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III. Intelligence Information for CVE-2021-21703

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Vendor Advisories for CVE-2021-21703 (5)

Mailing List Discussions for CVE-2021-21703 (4)

Other References for CVE-2021-21703 (1)

IV. Related Vulnerabilities

Same product: PHP
Same vendor: PHP Group
Same weakness: CWE-787

V. Comments for CVE-2021-21703

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