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Facebook CVE-2021-24045

CRITICAL
Access of Resource Using Incompatible Type (Type Confusion) (CWE-843)
2021-12-13 cve-assign@fb.com
9.8
CVSS 3.1 · NVD
View

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Type safety enforcement
MITRE ATT&CK

1 technique across 1 tactic: Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Impact

CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required.

Exploit ScenarioDerived

A remote attacker could execute arbitrary code by exploiting type confusion in the application by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
Patch available 1.2% exploitation probability (EPSS)

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AnalysisAI

A type confusion vulnerability could be triggered when resolving the "typeof" unary operator in Facebook Hermes prior to v0.10.0. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Access of Resource Using Incompatible Type (Type Confusion) vulnerability could allow attackers to execute arbitrary code by exploiting type confusion in the application.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Enforce strict type checking, use type-safe languages, validate object types before operations.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Access of Resource Using Incompatible Type (Type Confusion) (CWE-843), which allows attackers to execute arbitrary code by exploiting type confusion in the application. A type confusion vulnerability could be triggered when resolving the "typeof" unary operator in Facebook Hermes prior to v0.10.0. Note that this is only exploitable if the application using Hermes permits evaluation of untrusted JavaScript. Hence, most React Native applications are not affected. Affected products include: Facebook Hermes.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

DescriptionNVD

A type confusion vulnerability could be triggered when resolving the "typeof" unary operator in Facebook Hermes prior to v0.10.0. Note that this is only exploitable if the application using Hermes permits evaluation of untrusted JavaScript. Hence, most React Native applications are not affected.

Threat Intelligence Overview

EPSS Score
1.2%
Top 35% exploitable
Data Quality
3 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 1.2%
Patch available Yes
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact· derived
Medium

Priority Score

50
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +49
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Affected Products (CPE)NVD

cpe:2.3:a:facebook:hermes:*:*:*:*:*:*:*:*
CVE-2025-55182 CRITICAL POC
10.0 Dec 03

React Server Components in React 19.x contain a critical pre-authentication remote code execution vulnerability (CVE-202

CVE-2023-44487 HIGH POC
7.5 Oct 10

Denial of service against HTTP/2 server implementations allows remote unauthenticated attackers to exhaust server resour

CVE-2023-45239 CRITICAL POC
9.8 Oct 06

A lack of input validation exists in tac_plus prior to commit 4fdf178 which, when pre or post auth commands are enabled,

CVE-2021-24040 CRITICAL POC
9.8 Sep 10

Due to use of unsafe YAML deserialization logic, an attacker with the ability to modify local YAML configuration files c

CVE-2021-24218 HIGH POC
8.8 Apr 12

The wp_ajax_save_fbe_settings and wp_ajax_delete_fbe_settings AJAX actions of the Facebook for WordPress plugin before 3

CVE-2021-24217 HIGH POC
8.1 Apr 12

The run_action function of the Facebook for WordPress plugin before 3.0.0 deserializes user supplied data making it poss

CVE-2021-24028 CRITICAL
9.8 Apr 14

An invalid free in Thrift's table-based serialization can cause the application to crash or potentially result in code e

CVE-2016-6870 CRITICAL
9.8 Feb 17

Out-of-bounds write in the (1) mb_detect_encoding, (2) mb_send_mail, and (3) mb_detect_order functions in Facebook HHVM

CVE-2016-6875 CRITICAL
9.8 Feb 17

Infinite recursion in wddx in Facebook HHVM before 3.15.0 allows attackers to have unspecified impact via unknown vector

CVE-2016-6874 CRITICAL
9.8 Feb 17

The array_*_recursive functions in Facebook HHVM before 3.15.0 allows attackers to have unspecified impact via unknown v

CVE-2016-6873 CRITICAL
9.8 Feb 17

Self recursion in compact in Facebook HHVM before 3.15.0 allows attackers to have unspecified impact via unknown vectors

CVE-2016-6872 CRITICAL
9.8 Feb 17

Integer overflow in StringUtil::implode in Facebook HHVM before 3.15.0 allows attackers to have unspecified impact via u

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