// For flags

CVE-2021-21708

UAF due to php_filter_float() failing

Severity Score

9.8
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

1
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

In PHP versions 7.4.x below 7.4.28, 8.0.x below 8.0.16, and 8.1.x below 8.1.3, when using filter functions with FILTER_VALIDATE_FLOAT filter and min/max limits, if the filter fails, there is a possibility to trigger use of allocated memory after free, which can result it crashes, and potentially in overwrite of other memory chunks and RCE. This issue affects: code that uses FILTER_VALIDATE_FLOAT with min/max limits.

En PHP versiones 7.4.x anteriores a 7.4.28, versiones 8.0.x anteriores a 8.0.16 y versiones 8.1.x anteriores a 8.1.3, cuando son usados funciones de filtrado con el filtro FILTER_VALIDATE_FLOAT y los límites mínimo/máximo, si el filtro falla, se presenta la posibilidad de que sea activado el uso de la memoria asignada después de liberarla, lo que puede resultar en un bloqueo, y potencialmente la sobreescritura de otros trozos de memoria y RCE. Este problema afecta a: el código que usa FILTER_VALIDATE_FLOAT con límites mín/máx.

A flaw was found in PHP. The vulnerability occurs due to the malformed php_filter_float() function and leads to a use-after-free vulnerability. This flaw allows an attacker to inject a malicious file, leading to a crash or a Segmentation fault.

An update for the php:7.4 module is now available for Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support, Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions, and Red Hat Enterprise Linux 8.6 Telecommunications Update Service. Issues addressed include a use-after-free vulnerability.

*Credits: dukk at softdev dot online
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
Low
Attack Vector
Network
Attack Complexity
Medium
Authentication
None
Confidentiality
Partial
Integrity
Partial
Availability
Partial
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2021-01-04 CVE Reserved
  • 2022-02-27 CVE Published
  • 2024-09-17 CVE Updated
  • 2024-09-17 First Exploit
  • 2025-03-30 EPSS Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
CWE
  • CWE-416: Use After Free
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Php
Search vendor "Php"
 Php
Search vendor "Php" for product "Php"
 >= 7.4.0 < 7.4.28
Search vendor "Php" for product "Php" and version " >= 7.4.0 < 7.4.28"
-
Affected
Php
Search vendor "Php"
 Php
Search vendor "Php" for product "Php"
 >= 8.0.0 < 8.0.16
Search vendor "Php" for product "Php" and version " >= 8.0.0 < 8.0.16"
-
Affected
Php
Search vendor "Php"
 Php
Search vendor "Php" for product "Php"
 >= 8.1.0 < 8.1.3
Search vendor "Php" for product "Php" and version " >= 8.1.0 < 8.1.3"
-
Affected