CVE-2026-109719

Executive Summary

CVE-2026-109719 is a race condition leading to a use-after-free vulnerability in the Graphics: CanvasWebGL component of Mozilla Firefox, Firefox ESR 115, and Firefox ESR 153. An attacker who can entice a victim into loading a crafted web page could trigger memory corruption via concurrent WebGL operations, potentially resulting in arbitrary code execution within the browser's sandboxed content process. The vulnerability is addressed in Firefox 158, Firefox ESR 115.43, and Firefox ESR 153.5; no public proof-of-concept, exploit code, or CISA KEV listing is currently available.

Technical Analysis

The vulnerability resides in the CanvasWebGL component of Mozilla Firefox. The NVD description identifies a race condition that culminates in a use-after-free (UAF) condition. In the context of WebGL, a race condition typically arises when multiple asynchronous operations — such as context creation, resource allocation, buffer binding, or texture manipulation — manipulate a shared object concurrently. If the object is freed by one code path while another still holds a reference to it, subsequent dereferencing of that stale pointer results in a use-after-free.

Because the vulnerable component is the graphics subsystem directly accessible from JavaScript via the Canvas and WebGL APIs, the attack surface is the browser's web-content rendering pipeline. An attacker only needs to host or inject a malicious page that exercises the WebGL APIs in a way that wins the race. The resulting memory corruption occurs inside the content process, which is a primary target for sandbox-escape chains: a content-process code execution primitive can be chained with a separate sandbox escape to achieve full-system compromise.

The NVD description does not disclose the specific functions, objects, or code paths involved, and no CWE identifier, CVSS vector, or affected-version list was provided in the source data. Technical attribution of the exact faulty operation (for example, which WebGL object is freed prematurely) is therefore not possible from the available information. The classification as CWE-416 (Use After Free) reflects the described impact; the race condition is the causal trigger.

Given that Mozilla shipped fixes across three release branches (rapid release 158 and ESR 115.43 / ESR 153.5), the issue was present in a broad range of Firefox deployments, including the long-lived ESR channels widely used in enterprise and government environments.

Exploitation Scenarios

No public proof-of-concept exists; the attack chain below is inferred strictly from the vulnerability class (race condition → use-after-free in CanvasWebGL).

1. Reconnaissance / target identification. The attacker identifies victims running Firefox versions below 158, or Firefox ESR below 115.43 / 153.5. No server-side fingerprinting is required because the exploit is delivered through normal web browsing; the attacker simply needs the victim to load the crafted page. Delivery can occur through a compromised website, malicious advertisement, or phishing link.

2. Triggering the flaw class. The malicious page executes JavaScript that invokes WebGL operations designed to race against each other. By repeatedly and rapidly interleaving calls that allocate, bind, and release graphics resources, the attacker attempts to cause one code path to free an object while another code path still references it. Winning the race produces a dangling pointer.

3. Payload / execution method. Once the use-after-free is triggered, the attacker reclaims the freed memory with attacker-controlled data, causing the stale reference to point to a corrupted object. At the vulnerability-class level, this yields memory corruption that can be leveraged for control-flow manipulation within the content process. The exact exploitation primitive is unspecified in the source data and is not fabricated here.

4. Post-exploitation impact. Successful exploitation yields code execution inside the Firefox content process. From there, an attacker would need a separate sandbox-escape vulnerability to break out of the content process and reach the underlying operating system. Even without sandbox escape, a reliable UAF in the rendering process can cause crashes and denial of service, and in combination with other bugs it forms part of a full exploit chain.

Impact Assessment

Because CanvasWebGL is reachable from any web page, the vulnerability is remotely triggerable and requires user interaction (loading the malicious content). The most likely impact is arbitrary code execution in the browser content process, with potential for browser crashes (denial of service) if exploitation fails. The blast radius depends on deployment: unpatched Firefox and long-lived ESR installations in enterprise environments are exposed to drive-by attacks. CVSS is unavailable from the source data (N/A); a representative vector of CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H is provided as an analytical estimate consistent with the vulnerability class, reflecting high attack complexity (race condition), required user interaction, and high confidentiality/integrity/availability impact post-exploitation. This estimate should not be treated as an authoritative score.

Detection Guidance

Sigma Rule

title: Suspicious Firefox Content Process Crash or Memory Corruption Indicators
id: 8f3c2b1a-1097-49c2-9e7a-firefoxcve109719
status: experimental
description: Detects Firefox content-process crash patterns consistent with CVE-2026-109719 WebGL use-after-free exploitation attempts.
logsource:
  category: application
  product: windows
detection:
  selection_process:
    Image|endswith: '\\firefox.exe'
  selection_error:
    - 'EXCEPTION_ACCESS_VIOLATION'
    - 'EXCEPTION_HEAP_CORRUPTION'
    - 'use-after-free'
  condition: selection_process and selection_error
fields:
  - CommandLine
  - ParentImage
  - User
falsepositives:
  - Legitimate graphics driver crashes
level: medium

YARA Rule

rule CVE_2026_109719_Firefox_WebGL_UAF
{
    meta:
        description = "Heuristic detection of WebGL race-condition/UAF exploitation artifacts in Firefox"
        author = "Threat Intelligence"
        reference = "CVE-2026-109719"
        date = "2026-01-01"
    strings:
        $webgl1 = "getContext(\"webgl\")" ascii nocase
        $webgl2 = "getContext(\"webgl2\")" ascii nocase
        $c1 = "CanvasWebGL" ascii nocase
    condition:
        uint16(0) != 0x5A4D and any of ($webgl*) and $c1
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-109719 Possible Firefox WebGL UAF Exploit Attempt"; flow:established,to_client; content:"getContext"; http_client_body; content:"webgl"; http_client_body; nocase; threshold:type both, track by_src, count 20, seconds 10; classtype:attempted-user; sid:2026109719; rev:1;)

Elastic Detection

process where process.name == "firefox.exe" and
  (process.command_line like~ "*webgl*" or process.command_line like~ "*CanvasWebGL*")

Splunk SPL Query

index=endpoint (process_name="firefox.exe" OR process_name="firefox")
(Message="EXCEPTION_ACCESS_VIOLATION" OR Message="*use-after-free*" OR Message="*CanvasWebGL*")
| stats count by host, user, Message
| where count > 1

Wazuh OSSEC Rule

<group name="firefox,cve-2026-109719,">
  <rule id="109719" level="10">
    <decoded_as>windows_eventchannel</decoded_as>
    <field name="win.system.providerName">Application Error</field>
    <match>firefox.exe</match>
    <regex>EXCEPTION_ACCESS_VIOLATION|heap corruption|use-after-free</regex>
    <description>CVE-2026-109719: Possible Firefox WebGL use-after-free exploitation (process crash)</description>
    <mitre>
      <id>T1203</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). No CVE-specific workaround, vendor fix reference, or affected-version list was supplied in the source data.

1. Immediate mitigations. Upgrade Firefox to 158 or later. Upgrade Firefox ESR 115 to 115.43 or later, and Firefox ESR 153 to 153.5 or later. Where immediate upgrade is not possible, restrict browsing to trusted sites, disable or block WebGL via enterprise policy/site permissions, and keep other browser hardening (site isolation, content-process sandboxing) enabled. Note that disabling WebGL may break legitimate web applications and is a compensating control, not a fix.
2. Patch/upgrade steps. Deploy the vendor updates through your standard endpoint and software-management channels. Verify ESR channel versions explicitly, as ESR deployments often lag the rapid-release channel and are the primary residual exposure.
3. Long-term hardening. Maintain browser auto-update, enforce short patch SLAs for browsers, monitor Mozilla security advisories, and layer exploit mitigations (OS-level mitigations, EDR behavioral detections on browser crashes and child-process anomalies) to reduce the impact of future memory-corruption bugs.

References

• NVD entry for CVE-2026-109719: https://nvd.nist.gov/vuln/detail/CVE-2026-109719
• Mozilla Security Advisories (Firefox 158 / ESR 115.43 / ESR 153.5): https://www.mozilla.org/en-US/security/advisories/
• Mozilla Foundation Security Advisory index: https://www.mozilla.org/security/advisories/
• CWE-416 Use After Free: https://cwe.mitre.org/data/definitions/416.html
• MITRE ATT&CK T1203 Exploitation for Client Execution: https://attack.mitre.org/techniques/T1203/

No threat actor campaign or in-the-wild exploitation evidence is available for this CVE in the provided data; it is not listed in CISA KEV.