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CVE-2023-7101Spreadsheet::ParseExcel Remote Code Execution Vulnerability

Patch nowHigh7.8Exploited, CISA due date 2024-01-23EPSS 19%, higher than 97% of scored CVEs

CVE-2023-7101 is a code injection in Spreadsheet::ParseExcel, 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

Input is evaluated as code by the application, so an attacker's code runs inside it. Input reaches an eval-style call and runs as code.

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 run commands or code with the privileges of the affected service.

Is it being exploited?

CISA added it to the Known Exploited Vulnerabilities catalog on 2024-01-02: it is being exploited in the wild. EPSS estimates a 19% chance of exploitation activity in the next 30 days, higher than 97% 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: 2024-01-23.
  2. Apply the fix for Spreadsheet::ParseExcel: the patch and release notes are linked below.
  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

Spreadsheet::ParseExcel version 0.65 is a Perl module used for parsing Excel files. Spreadsheet::ParseExcel is vulnerable to an arbitrary code execution (ACE) vulnerability due to passing unvalidated input from a file into a string-type “eval”. Specifically, the issue stems from the evaluation of Number format strings (not to be confused with printf-style format strings) within the Excel parsing logic.

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

  • Operating systems on servers, workstations or devices. Everything on the host inherits the flaw.
  • Application servers and the hosts they run on. The flaw sits between untrusted input and code or command execution.
  • Template engines. The flaw sits between untrusted input and code or command execution.

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.
  • Between untrusted input and code or command execution. An attacker who crosses it can run commands or code with the privileges of the affected service.

Questions to answer about your own systems

  • Where does Spreadsheet::ParseExcel 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.