CVE-2025-1414: Mozilla Firefox RCE Vulnerability

CVE-2025-1414 Overview

CVE-2025-1414 covers memory safety bugs present in Mozilla Firefox 135. Mozilla developers identified internal memory corruption issues during routine testing of the browser engine. Some of these bugs showed evidence of memory corruption, and Mozilla presumes that with enough effort some could have been exploited to run arbitrary code. The issue is classified under [CWE-787] Out-of-Bounds Write. Mozilla resolved the defects in Firefox 135.0.1 through the Mozilla Security Advisory MFSA-2025-12.

Critical Impact
Memory corruption in Firefox 135 could be leveraged by a crafted web page to compromise integrity and availability of the browser process, with potential for arbitrary code execution.

Affected Products

Mozilla Firefox 135 (all builds prior to 135.0.1)
Mozilla Firefox desktop releases on Windows, macOS, and Linux
Downstream distributions packaging Firefox 135

Discovery Timeline

2025-02-18 - CVE-2025-1414 published to the National Vulnerability Database
2026-04-13 - Last updated in NVD database

Technical Details for CVE-2025-1414

Vulnerability Analysis

The advisory groups multiple memory safety defects identified in the Firefox 135 codebase. The issues map to [CWE-787] Out-of-Bounds Write, indicating that the browser writes data past the bounds of an allocated buffer. Out-of-bounds writes in a browser engine can corrupt adjacent heap structures, function pointers, or object metadata.

Mozilla states that some defects showed evidence of memory corruption. Skilled attackers can often convert such corruption into arbitrary code execution by shaping heap allocations and overwriting control data. Because Firefox processes untrusted content from any visited site, the attack surface includes the JavaScript engine, layout, graphics, and media subsystems.

Exploitation requires no authentication and no user interaction beyond visiting attacker-controlled content. The browser sandbox limits the immediate blast radius, but a successful write primitive remains a foundation for sandbox escape chains.

Root Cause

The root cause is improper bounds enforcement in one or more native components of Firefox 135. Mozilla has not published a per-bug breakdown in the public advisory, instead consolidating the defects in MFSA-2025-12 and the tracking entry Mozilla Bug Report #1943179. The fix landed in Firefox 135.0.1.

Attack Vector

An attacker hosts a crafted web page or delivers malicious content through an embedded frame or advertisement. When a user running Firefox 135 loads the content, the rendering pipeline triggers the unsafe write. No credentials, prompts, or local access are required. The vulnerability mechanism is described in prose only; no public proof-of-concept code is available.

Detection Methods for CVE-2025-1414

Indicators of Compromise

Unexpected firefox.exe or firefox process crashes with access violation or segmentation fault signatures on systems running build 135.
Child content processes spawning unusual descendants such as command interpreters or scripting hosts.
Outbound connections from Firefox to newly registered or low-reputation domains immediately after browsing activity.

Detection Strategies

Inventory installed Firefox versions across managed endpoints and flag any host still running a build earlier than 135.0.1.
Monitor crash telemetry and Windows Error Reporting or core dump artifacts for repeated Firefox content-process faults.
Correlate browser process anomalies with web proxy logs to identify the originating URL or domain.

Monitoring Recommendations

Ingest endpoint process, file, and network telemetry into a centralized analytics platform to detect post-exploitation behavior originating from browser processes.
Alert on Firefox spawning non-browser child processes, a behavior consistent with sandbox escape attempts.
Track DNS and TLS connections from Firefox to domains with low age or reputation scores.

How to Mitigate CVE-2025-1414

Immediate Actions Required

Upgrade all Firefox 135 installations to Firefox 135.0.1 or later without delay.
Push the update through enterprise management tooling such as Group Policy, Intune, Jamf, or configuration management for Linux.
Validate the installed version on each endpoint after deployment using firefox --version.

Patch Information

Mozilla released the fix in Firefox 135.0.1. Patch details and full advisory text are available in the Mozilla Security Advisory MFSA-2025-12 and the tracking record Mozilla Bug Report #1943179.

Workarounds

Restrict browsing on unpatched hosts to a curated allowlist of trusted internal sites until the update is applied.
Disable JavaScript on untrusted sites through about:config or enterprise policy to reduce the exploitable surface.
Deploy network-level content filtering to block known malicious domains and high-risk advertising networks.

bash

# Configuration example: enforce minimum Firefox version via enterprise policy (policies.json)
{
  "policies": {
    "DisableAppUpdate": false,
    "AppAutoUpdate": true,
    "OverrideFirstRunPage": "",
    "DisableTelemetry": false
  }
}