php php CVE-2021-21703 vulnerability in PHP and Other Products
Published on October 25, 2021

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

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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.

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Vulnerability Analysis

CVE-2021-21703 can be exploited with local system access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.

Attack Vector:
LOCAL
Attack Complexity:
HIGH
Privileges Required:
LOW
User Interaction:
NONE
Scope:
CHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
HIGH

Weakness Types

What is a Memory Corruption Vulnerability?

The software writes data past the end, or before the beginning, of the intended buffer. Typically, this can result in corruption of data, a crash, or code execution. The software may modify an index or perform pointer arithmetic that references a memory location that is outside of the boundaries of the buffer. A subsequent write operation then produces undefined or unexpected results.

CVE-2021-21703 has been classified to as a Memory Corruption vulnerability or weakness.

What is an Authorization Vulnerability?

The software does not restrict or incorrectly restricts access to a resource from an unauthorized actor.

CVE-2021-21703 has been classified to as an Authorization vulnerability or weakness.


Products Associated with CVE-2021-21703

You can be notified by email with stack.watch whenever vulnerabilities like CVE-2021-21703 are published in these products:

PHP
 
Debian Linux
 
Fedora Project Fedora
 
NetApp Clustered Data Ontap
 
Oracle Communications Diameter Signaling Router
 

Affected Versions

PHP Group PHP:

Exploit Probability

EPSS
0.13%
Percentile
32.99%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.