External risk intelligence

WinRAR Code Execution Risk From Malicious Archives.

CVE advisoryKnown Exploit

CVE-2023-38831

A vulnerability in WinRAR allows for arbitrary code execution when a user opens a crafted ZIP archive. This could impact organizations by compromising systems and data. Active exploitation was observed from April to October 2023.

1Halo Surface Signal

Rarlab Winrar

before 6.23

External exposure likelihood

Halo Surface Signal score for CVE-2023-38831

WinRAR is a desktop application used locally by end users to manage files. It is not an internet-facing service, gateway, or network appliance, and it does not maintain a public-facing listener or remote management interface by design. The vulnerability requires a user to manually open a specifically crafted local file, confirming the attack surface is not reachable via the public internet.

Horizon Alert

Summary of the vulnerability and why it matters

RARLAB WinRAR has a vulnerability that allows for arbitrary code execution. This occurs when a user attempts to view a legitimate file within a specially crafted ZIP archive. The flaw lies in how the software processes files and folders with identical names, potentially leading to the execution of unintended code.

Vulnerable component: RARLAB WinRAR
Core weakness: Malicious code execution via archive processing
Main business impact: Unauthorized code execution on user systems

Attack Path

How an attacker could exploit the issue

A vulnerability in WinRAR allows an attacker to execute arbitrary code by tricking a user into opening a specially crafted ZIP archive. This archive can contain a benign file and a folder with the same name. When a user attempts to access the benign file, the executable content within the folder is processed, leading to code execution. This vulnerability was actively exploited in the wild between April and October 2023.

Archive requires specific file/folder structure.
Attacker provides malicious archive to user.
User opens archive; code executes.

Live Threat

Current exploitation, exposure, and threat context

Exploitants of this vulnerability could execute arbitrary code on a user's system by tricking them into opening a specially crafted ZIP archive. This attack method was observed in the wild between April and October 2023, targeting users by presenting seemingly harmless files alongside malicious content within archives. Organizations using affected versions of WinRAR face risks to their systems and data integrity.

Low skill attackers.
User opens crafted ZIP.
High risk; treat as urgent.

Priority actions

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability presents a risk to organizations by enabling attackers to execute arbitrary code on user systems. The exploitation involves users attempting to view a benign file within a specially crafted ZIP archive, leading to the processing of executable content from a similarly named folder. This issue has been observed in the wild and could impact the confidentiality, integrity, and availability of affected systems.

Identify all deployed instances of the affected software.
Isolate systems or restrict archive handling.
Implement the vendor-provided update and confirm its success.

Frequently asked questions

What is RARLAB WinRAR and what is its primary function?

RARLAB WinRAR is a file archiving and compression tool. It enables users to create, extract, and manage various archive formats, most notably RAR and ZIP. Its common uses include reducing file sizes for storage or transfer and consolidating multiple files into a single package.

What type of vulnerability is CVE-2023-38831 in WinRAR?

CVE-2023-38831 is a critical vulnerability in WinRAR. It allows for arbitrary code execution. This occurs when a user tries to open a seemingly harmless file, like a JPG, within a ZIP archive that has been specially crafted. The archive contains both the benign file and a folder with the identical name, leading to the execution of malicious code.

How does an attacker exploit the WinRAR vulnerability?

An attacker exploits this vulnerability by creating a malicious ZIP archive. This archive contains a benign file and a folder with the same name. When a user attempts to access the benign file, WinRAR processes the contents of the folder, which can include executable code, leading to arbitrary code execution on the user's system.

What is the relevance of CVE-2023-38831 concerning the Halo Surface Signal?

The Halo Surface Signal indicates that CVE-2023-38831 is very unlikely to be exploited against internet-facing systems. This is because WinRAR is a local desktop application, and the vulnerability requires a user to manually open a specially crafted file, meaning the attack surface is not accessible from the public internet.

What practical steps should be taken to address the WinRAR vulnerability?

To address this vulnerability, organizations should first identify all systems running affected versions of WinRAR. Implementing vendor-provided updates is crucial. If immediate updates are not possible, consider isolating affected systems or restricting how archives are handled until the software can be updated to a secure version.

References

Cyber Threat Intelligence (CTI)

Sources: malpedia, threatActor

Written by Nicholas Merritt

External-surface CVE analysis and Halo Surface Signal prioritization for Halo Threat Intelligence.