CVE-2024-9680

What it actually does

This vulnerability is a use-after-free flaw in Mozilla Firefox Animation Timeline handling. A malicious web page can trigger unsafe memory reuse in the browser content process and execute attacker-controlled code with the privileges of that process. Because the bug is in the browser rendering/content path, exploitation can occur through normal browsing activity without requiring the user to install software. Full device compromise may require chaining with a sandbox escape or privilege-escalation vulnerability, but code execution in the content process is already sufficient for data theft from browser-accessible contexts and follow-on exploitation. Mozilla reported active exploitation in the wild.

Why it matters to the business

Organizations with unpatched Firefox or Firefox ESR installations face a high-priority risk of drive-by compromise from malicious or compromised websites. Since this issue is listed in CISA KEV, has been exploited in the wild, and is associated with ransomware-related activity, delayed patching increases the likelihood of endpoint compromise, credential theft, browser session theft, malware deployment, and business disruption. The CISA remediation due date of 2024-11-05 has passed, so any remaining exposure should be treated as overdue and urgent.

How an attack unfolds

An attacker prepares a web page containing JavaScript, CSS, or animation-related content that triggers the use-after-free condition in Firefox Animation Timeline processing. The victim is lured to the page through phishing, malvertising, watering-hole compromise, or a link embedded in email or messaging platforms. When the vulnerable browser renders the page, the attacker manipulates memory layout to reclaim freed memory with controlled data, redirect execution flow, and run code inside the Firefox content process. In a targeted campaign, the exploit may be chained with a sandbox escape, credential theft tooling, or malware loader to persist on the endpoint, steal browser data, or support ransomware intrusion activity. Reported exploitation in the wild means defenders should assume weaponized exploit code has existed outside controlled research environments.

How to fix it

Upgrade affected browsers immediately. Fixed versions are Firefox 131.0.2 or later, Firefox ESR 128.3.1 or later, and Firefox ESR 115.16.1 or later. Prefer centrally managed automatic browser updates and verify that ESR channels are patched separately from standard Firefox installations. Where immediate patching is not possible, reduce exposure by restricting access to untrusted websites, disabling use of vulnerable browsers for Internet access, using application control to block outdated Firefox binaries, and routing browsing through isolation technology. Mitigations should be considered temporary because the vulnerability is actively exploited and listed in CISA KEV with ransomware relevance.

How to confirm the fix worked

Confirm installed versions across endpoints and software inventory. Validate that standard Firefox is version 131.0.2 or later, Firefox ESR 128.x is 128.3.1 or later, and Firefox ESR 115.x is 115.16.1 or later. On endpoints, check browser About dialogs, package manager inventories, EDR software inventory, MDM records, or command-line version output where available. Confirm that outdated Firefox binaries are not still present in alternate install paths, user profiles, portable app directories, virtual desktop images, golden images, or unmanaged developer workstations. After remediation, test that update policies prevent rollback and that users cannot launch older copies of Firefox.

Typical attack path

1. Identify users or systems running Firefox versions earlier than 131.0.2, Firefox ESR versions earlier than 128.3.1, or Firefox ESR versions earlier than 115.16.1.
2. Deliver a malicious URL through phishing, malvertising, compromised legitimate websites, or watering-hole infrastructure.
3. Cause the victim's vulnerable Firefox browser to render crafted animation/timeline content.
4. Trigger the use-after-free condition and achieve code execution in the browser content process.
5. Optionally chain with a sandbox escape or local privilege escalation to gain broader access to the endpoint.
6. Steal browser-accessible data such as session tokens, credentials, cookies, or sensitive web application content.
7. Deploy follow-on payloads, establish persistence, move laterally, or support ransomware-related intrusion objectives.

How to detect it

To determine whether exploitation already occurred, correlate vulnerable Firefox usage with web browsing, crash telemetry, endpoint process activity, and network logs. Review browser history, proxy logs, DNS logs, EDR telemetry, and email security logs for visits to suspicious or newly registered domains shortly before Firefox crashes or abnormal process behavior. Examine Firefox crash reports for signatures involving animation timeline or content-process memory faults, especially on versions below the fixed releases. On Windows, review EDR and event logs for firefox.exe spawning unusual child processes such as cmd.exe, powershell.exe, wscript.exe, cscript.exe, mshta.exe, rundll32.exe, regsvr32.exe, or dropped executables. On macOS and Linux, look for firefox launching shells, curl/wget, Python, AppleScript, or other interpreters. Because browser memory-corruption exploits often leave few stable file-based artifacts, prioritize behavioral detections: vulnerable Firefox version plus suspicious URL access, content-process crash, unexpected child process, payload download, credential access, or persistence creation. Threat hunting should include activity associated with zero-day exploitation campaigns and ransomware intrusion chains, but no single public exploit URL or payload hash is universally reliable for this vulnerability.

• firefox.exe -> cmd.exe
• firefox.exe -> powershell.exe
• firefox.exe -> wscript.exe
• firefox.exe -> cscript.exe
• firefox.exe -> mshta.exe
• firefox.exe -> rundll32.exe
• firefox.exe -> regsvr32.exe
• firefox -> /bin/sh
• firefox -> /bin/bash
• firefox -> curl
• firefox -> wget
• firefox -> python
• firefox -> osascript
• Firefox < 131.0.2
• Firefox ESR < 128.3.1
• Firefox ESR < 115.16.1
• AnimationTimeline
• Animation timelines
• use-after-free
• content process crash
• minidumps
• Crash Reports

What your security team should do

• Treat this as an urgent patching item because it is actively exploited, listed in CISA KEV, associated with ransomware activity, and the KEV due date has passed.
• Immediately inventory Firefox and Firefox ESR installations across managed endpoints, VDI images, servers with GUI browsers, developer systems, and unmanaged bring-your-own-device populations where applicable.
• Patch to Firefox 131.0.2 or later, Firefox ESR 128.3.1 or later, or Firefox ESR 115.16.1 or later, depending on the deployed release channel.
• Use EDR, MDM, software management, or application control to block execution of known-outdated Firefox binaries until patching is complete.
• Prioritize forensic review for endpoints that ran vulnerable Firefox versions and showed suspicious browser crashes, visits to unknown external URLs, abnormal child processes, or post-browser-exploitation behavior.
• Hunt for follow-on activity such as credential dumping, suspicious downloads, new persistence mechanisms, unusual script execution, or ransomware precursor tooling on systems with vulnerable Firefox exposure.
• Educate users that browser restart is required after update and ensure managed update policies force relaunch where supported.