CVE-2026-16362: Firefox WebRTC Use-After-Free Vulnerability

CVE-2026-16362 Overview

CVE-2026-16362 is a use-after-free vulnerability [CWE-416] in the WebRTC Audio/Video component of Mozilla Firefox and Thunderbird. The flaw affects the real-time communication stack used for browser-based audio and video streaming. Mozilla addressed the issue in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13. An attacker who convinces a user to visit a crafted page can trigger memory corruption in the browser process. Successful exploitation can lead to arbitrary code execution within the affected application context.

Critical Impact
Remote attackers can achieve high-impact compromise of confidentiality, integrity, and availability through a crafted web page that abuses WebRTC audio/video handling, requiring only user interaction to load the content.

Affected Products

Mozilla Firefox versions prior to 153
Mozilla Firefox ESR versions prior to 140.13
Mozilla Thunderbird versions prior to 153 and 140.13

Discovery Timeline

2026-07-21 - CVE-2026-16362 published to NVD
2026-07-22 - Last updated in NVD database

Technical Details for CVE-2026-16362

Vulnerability Analysis

The vulnerability is a use-after-free condition [CWE-416] inside the WebRTC Audio/Video subsystem. WebRTC handles peer-to-peer audio and video streams and manages a complex lifecycle of media tracks, sessions, and native objects. A use-after-free occurs when code continues to reference a memory region after it has been freed. In browser contexts, this class of flaw frequently enables attackers to influence heap layout and gain control of a freed object's reused memory. The result is corruption of internal state that can be steered toward arbitrary read, write, or code execution primitives.

Root Cause

The root cause is improper object lifetime management within the WebRTC Audio/Video component. A pointer or reference to a media-related object is retained after the underlying allocation has been released. Subsequent operations dereference the stale pointer, allowing attacker-controlled data to be treated as a valid object. Refer to Mozilla Security Advisory MFSA-2026-68 and Mozilla Bug 2043188 for technical details.

Attack Vector

Exploitation is remote and requires user interaction. A victim must load a page that establishes or manipulates a WebRTC session under attacker control. The attacker then triggers the free-and-reuse sequence in the audio/video pipeline. No prior authentication is required, and the scope remains within the affected process. See MFSA-2026-70, MFSA-2026-71, and MFSA-2026-72 for advisory coverage across Firefox and Thunderbird branches.

No public proof-of-concept code is available for this vulnerability at the time of publication.

Detection Methods for CVE-2026-16362

Indicators of Compromise

Unexpected crashes or hangs of firefox.exe, firefox, or thunderbird processes referencing WebRTC modules in crash telemetry.
Browser child process termination with access violation or SIGSEGV signatures during active WebRTC sessions.
Outbound connections from browser processes to unfamiliar STUN, TURN, or signaling endpoints preceding a crash event.

Detection Strategies

Inventory endpoint browser versions and flag any Firefox below 153, Firefox ESR below 140.13, or Thunderbird below 153 or 140.13.
Correlate browser crash reports with recent navigation history to identify pages that consistently trigger faults in WebRTC code paths.
Monitor for child-process spawning or shellcode-like behavior originating from browser processes after WebRTC activity.

Monitoring Recommendations

Enable EDR telemetry on browser process trees, including module loads for WebRTC libraries and unusual memory allocations.
Ingest browser crash dumps into a central log platform and alert on faults involving media or WebRTC symbols.
Track user-agent and version data at web proxies to identify unpatched clients still in production.

How to Mitigate CVE-2026-16362

Immediate Actions Required

Update Firefox to version 153 or later on all endpoints.
Update Firefox ESR to version 140.13 or later where the ESR channel is deployed.
Update Thunderbird to version 153 or 140.13, depending on the release channel in use.
Restart affected applications after patching to ensure the vulnerable code is unloaded from memory.

Patch Information

Mozilla released fixes in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13. Details are published in MFSA-2026-68, MFSA-2026-70, MFSA-2026-71, and MFSA-2026-72. Administrators should deploy the vendor patches through their standard software distribution channels.

Workarounds

Disable WebRTC in enterprise policy where business use cases do not require peer-to-peer audio or video.
Restrict browsing to trusted sites through web filtering until patches are fully deployed.
Enforce least-privilege user contexts so that successful exploitation cannot easily escalate to system-level access.

bash

# Example Firefox enterprise policy to disable WebRTC peer connections
# Place in policies.json under the Firefox distribution directory
{
  "policies": {
    "Preferences": {
      "media.peerconnection.enabled": {
        "Value": false,
        "Status": "locked"
      }
    }
  }
}