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CVE-2023-38831RARLAB WinRAR Code Execution Vulnerability

Patch nowHigh7.8Exploited, CISA due date 2023-09-14EPSS 100%, higher than 100% of scored CVEs

CVE-2023-38831 is a insufficient verification of data authenticity in RARLAB WinRAR, rated high (7.8 on CVSS 3.1).

Why this priority: Exploited in the wild: listed in CISA's KEV catalog.

Published · Updated · NVD status: Analyzed

What it is

Data is accepted without proof it came from where it claims.

How it is reached

An attacker can exploit it by someone who can already run code or sign in on the machine, without an account, but someone has to act first, such as opening a file or following a link.

What an attacker gains

A successful attack can read the data it protects, change data or behaviour and take it offline. In practice, this kind of flaw lets an attacker read or tamper with traffic, or pass a forged message as genuine.

Is it being exploited?

CISA added it to the Known Exploited Vulnerabilities catalog on 2023-08-24: it is being exploited in the wild. CISA links it to ransomware campaigns. EPSS estimates a 100% chance of exploitation activity in the next 30 days, higher than 100% of scored CVEs.

What to do

  1. Treat it as urgent: it is on CISA's KEV list. CISA's deadline for US federal agencies: 2023-09-14.
  2. Upgrade RARLAB WinRAR to 6.23 or later.
  3. Limit who can run code or sign in on the hosts that run it.
  4. Warn the people who use it, and filter files and links on the way in.
  5. Check exposed instances for signs of compromise, not only for the version.

Description from NVD

RARLAB WinRAR before 6.23 allows attackers to execute arbitrary code when a user attempts to view a benign file within a ZIP archive. The issue occurs because a ZIP archive may include a benign file (such as an ordinary .JPG file) and also a folder that has the same name as the benign file, and the contents of the folder (which may include executable content) are processed during an attempt to access only the benign file. This was exploited in the wild in April through October 2023.

What this means for your architecture.

A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.

Components it touches

  • TLS termination and service-to-service channels. The flaw sits on the network path between clients and services.
  • Signature checks. The flaw sits on the network path between clients and services.

Trust boundaries in play

  • Host boundary. The attacker needs a foothold on the machine first; the flaw turns a small foothold into a bigger one.
  • People who open files and links. Mail, chat and browsers are the delivery path.
  • On the network path between clients and services. An attacker who crosses it can read or tamper with traffic, or pass a forged message as genuine.

Questions to answer about your own systems

  • Where does RARLAB WinRAR run in your systems, and at which version?
  • Which of those hosts also run code or users you do not fully trust?
  • What can it reach once compromised: which data stores, secrets and services?
See how Veriom maps an architectureTake the interactive tour

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Sources

  • CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
  • Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
  • Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
  • Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.