# Multiple Firefox vulnerabilities enable arbitrary code execution

Published: 2026-03-10 · Severity: routine
Canonical: https://vorant.io/reports/b695b87e-cf8c-50df-909d-90f9baba1d55/multiple-firefox-vulnerabilities-enable-arbitrary-code-execution

> Three Mozilla Firefox flaws including heap buffer overflow allow arbitrary code execution; not yet exploited in the wild.

Mozilla Firefox versions prior to 148.0.2 contain multiple vulnerabilities, the most severe of which enable arbitrary code execution via a heap buffer overflow in the Audio/Video component. The vulnerabilities include a same-origin policy bypass in CSS parsing and additional memory safety bugs. An attacker exploiting these flaws could install programs, view or modify data, or create new accounts with full user rights depending on the privileges of the affected user account. The article notes there are currently no reports of active exploitation in the wild. Patching to Firefox 148.0.2 or later is the primary mitigation, along with standard defenses including running browsers as non-privileged users, enabling exploit protection features, and restricting web-based content where feasible.

## Mentioned in this report

- Vulnerabilities: CVE-2026-3845, CVE-2026-3846, CVE-2026-3847

## Detection guidance (public sample)

### Firefox Spawning Command Shell or Script Interpreter on Windows

ATT&CK: T1189

Firefox (main or content process) spawning cmd, PowerShell, script hosts or LOLBins, which is consistent with browser exploitation leading to code execution after a drive-by visit. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.

```yaml
title: Firefox Spawning Command Shell or Script Interpreter on Windows
description: Detects firefox.exe spawning shells, script hosts or common LOLBins.
  Browser memory-corruption exploits (e.g. heap overflow in Audio/Video) that reach
  code execution typically pivot to a shell or script interpreter. Firefox itself
  rarely launches these.
tags:
- attack.initial-access
- attack.t1189
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    ParentImage|endswith: \firefox.exe
    Image|endswith:
    - \cmd.exe
    - \powershell.exe
    - \pwsh.exe
    - \wscript.exe
    - \cscript.exe
    - \mshta.exe
    - \rundll32.exe
    - \regsvr32.exe
    - \certutil.exe
    - \bitsadmin.exe
    - \msiexec.exe
    - \wmic.exe
  condition: selection
falsepositives:
- Custom enterprise protocol handlers or external-application launchers configured
  to run via cmd.exe from Firefox
- Developers using browser extensions with native messaging hosts implemented as scripts
level: high
id: d82f5fa8-26f3-5ffe-bcdf-4ac488b87f66
status: experimental
author: Vorant
references:
- https://www.cisecurity.org/advisory/multiple-vulnerabilities-in-mozilla-firefox-could-allow-for-arbitrary-code-execution_2026-022
```

### Firefox Spawning Shell or Network Tool on Linux

ATT&CK: T1189

Firefox spawning an interactive shell, scripting runtime or network utility on Linux, suggesting post-exploitation after a browser compromise. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.

```yaml
title: Firefox Spawning Shell or Network Tool on Linux
description: Detects Firefox parent processes launching shells, scripting runtimes
  or download/network utilities on Linux, a pattern consistent with code execution
  following exploitation of a browser vulnerability via a malicious web page.
tags:
- attack.initial-access
- attack.t1189
logsource:
  category: process_creation
  product: linux
detection:
  selection_parent:
    ParentImage|endswith:
    - /firefox
    - /firefox-bin
    - /firefox-esr
  selection_child:
    Image|endswith:
    - /nc
    - /ncat
    - /netcat
    - /curl
    - /wget
    - /python
    - /python3
    - /perl
    - /socat
    - /bash
    - /dash
    - /zsh
  condition: selection_parent and selection_child
falsepositives:
- Firefox wrapper or launcher scripts that invoke bash or dash during startup under
  some distributions
- Custom MIME or protocol handlers configured to launch scripts from Firefox
level: medium
id: a556380b-dfd7-5a15-b9ad-dd2e2b26a84a
status: experimental
author: Vorant
references:
- https://www.cisecurity.org/advisory/multiple-vulnerabilities-in-mozilla-firefox-could-allow-for-arbitrary-code-execution_2026-022
```

Behavioural rules are generated from public reporting — validate in your environment before deploying.

Source reporting: https://www.cisecurity.org/advisory/multiple-vulnerabilities-in-mozilla-firefox-could-allow-for-arbitrary-code-execution_2026-022

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