CVE-2026-109774

Executive Summary

CVE-2026-109774 is a memory-safety vulnerability in the DOM: Notifications component of Mozilla Firefox, caused by an invalid pointer leading to undefined behavior. The flaw is fixed in Firefox 158, meaning all earlier Firefox releases are presumed affected. Successful exploitation as a memory-corruption class issue can potentially result in a renderer process crash or, depending on heap layout, arbitrary code execution within the browser's sandboxed content process, posing a risk to any user browsing attacker-controlled content.

Technical Analysis

The vulnerability class, per the NVD description, is an "invalid pointer" resulting in "undefined behavior" within the DOM: Notifications component of Firefox. This maps to memory-safety weaknesses (dangling, uninitialized, or otherwise invalid pointers) that trigger undefined behavior at the C/C++ level when the browser processes notification-related DOM operations.

The attack surface is the Notifications DOM API that web content can invoke to request and interact with system notifications. Because web pages can reach this component, a malicious page could drive the affected code path. However, the provided intelligence does not disclose the specific function, method, object, or memory state involved, nor the precise sequence required to produce the invalid pointer. No code-level detail beyond "invalid pointer / undefined behavior" is available.

Given the undefined-behavior classification, the practical manifestation is unpredictable: it may be observed primarily as a crash (denial of service of the affected process), or, when memory layout is attacker-influenced, as memory corruption with potential for code execution. No CVSS vector or CWE identifier was supplied; the CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) mapping reflects the memory-safety nature of the flaw and should be treated as a class-level characterization, not a confirmed vendor assignment. No affected version list, package data, or vendor advisory detail is available in the provided data.

Exploitation Scenarios

1. Reconnaissance/target identification: An adversary identifies users running Firefox versions below 158, or lures them to attacker-controlled pages.
2. Triggering the flaw: The victim loads a page that exercises the DOM: Notifications component, invoking notification-related DOM operations that reach the vulnerable code path and cause the invalid pointer/undefined behavior.
3. Execution method: No public PoC exists and no specific function, parameter, or trigger sequence is disclosed in the provided data. At the vulnerability-class level, an attacker would need to craft content that drives notification DOM handling into the invalid-pointer state; precise payload construction cannot be described without implementation details.
4. Post-exploitation impact: Best case for the attacker is reliable code execution in the content process; even absent that, triggering the undefined behavior can crash the process (denial of service). No exploit code, Nuclei template, or in-the-wild evidence is available. The attack chain beyond step 2 is inferred from the memory-corruption vulnerability class.

Impact Assessment

Impact scope is any user running Firefox < 158 who visits malicious or compromised content that reaches the Notifications DOM path. Blast radius is bounded by Firefox's process sandbox (content/renderer isolation), which constrains but does not eliminate risk: a renderer compromise still exposes user data, session tokens, and can be chained with a sandbox-escape to gain full host access. As a client-side browser flaw, it is not remotely exploitable against a server; there is no public-facing service component. Because no CVSS score or subscores were provided, no quantitative impact rating can be assigned; CISA KEV status is NO, and no EPSS score is available. Exploitation requires user interaction (browsing to crafted content), which moderates mass-exploitation likelihood, but the potential for code execution keeps severity potentially high once a working trigger is developed.

Detection Guidance

Sigma Rule

title: Suspicious Firefox Renderer Crash Correlated with Notification DOM Activity
id: 7c1f2a94-3b6e-4d21-9f80-1a2b3c4d5e6f
status: experimental
description: Detects repeated Firefox content-process crashes, potentially indicating exploitation attempts of a DOM Notifications memory-safety flaw (CVE-2026-109774).
logsource:
  category: process_creation
  product: windows
detection:
  selection_image:
    Image|endswith:
      - '\firefox.exe'
  selection_crash:
    CommandLine|contains:
      - 'crashreporter'
      - 'MOZ_CRASH'
  condition: selection_image and selection_crash
fields:
  - CommandLine
  - Image
falsepositives:
  - Legitimate browser crashes unrelated to exploitation
level: low
tags:
  - attack.t1190

YARA Rule

rule CVE_2026_109774_Firefox_Notification_UAF
{
    meta:
        description = "Class-level heuristic for Firefox builds predating 158 handling DOM Notification operations; indicative only"
        author = "Threat Intelligence"
        reference = "CVE-2026-109774"
        date = "2026-01-01"
    strings:
        $notif1 = "Notification" ascii wide
        $dom1   = "nsDOMNotification" ascii wide
        $ver    = /Firefox\/(1[0-5][0-9]|[0-9][0-9]?)\./ ascii
    condition:
        (uint16(0) == 0x5A4D or uint32(0) == 0x464C457F) and
        any of ($notif*) and not $ver
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-109774 Potential Firefox Notification DOM Exploit Attempt"; flow:established,to_client; content:"Mozilla"; http_user_agent; content:"Firefox/"; http_user_agent; pcre:"/Firefox\/(?:[0-9]|[1-9][0-9]|1[0-5][0-9])\./U"; threshold:type both, track by_src, count 5, seconds 60; classtype:attempted-user; sid:2026109774; rev:1;)

Elastic Detection

process where process.name == "firefox.exe" and process.command_line like~ "*MOZ_CRASH*"

Splunk SPL Query

index=endpoint (process_name="firefox.exe" OR process_name="firefox")
| where match(user_agent, "Firefox/(?:[0-9]|[1-9][0-9]|1[0-5][0-9])\.")
| stats count values(dest) as targets by src_ip, user_agent
| where count > 3

Wazuh OSSEC Rule

<group name="firefox,cve-2026-109774,">
  <rule id="109774" level="5">
    <decoded_as>json</decoded_as>
    <field name="process.name">firefox|firefox.exe</field>
    <match>MOZ_CRASH|crashreporter|invalid pointer|undefined behavior</match>
    <description>CVE-2026-109774: Possible Firefox Notification DOM memory-safety crash/exploitation.</description>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source in the data provided). The NVD description states the issue "was fixed in Firefox 158," but no vendor advisory, patch source, or affected-version list was supplied; treat this as the target version rather than a confirmed tracked patch.

1. Immediate mitigations: Restrict browsing of untrusted content; enforce enterprise browser policy to block untrusted sites; enable site isolation and keep notification permissions disabled for untrusted origins; monitor for repeated renderer crashes as a possible indicator of exploitation attempts.
2. Patch/upgrade steps: Upgrade Firefox to version 158 or later as stated in the NVD description. Verify version via the browser's about dialog and manage updates through your enterprise deployment channel. If an ESR/managed channel is used, confirm with the vendor channel mapping before rollout.
3. Long-term hardening: Maintain rapid patching for browsers, standardize on a current supported Firefox release, deploy renderer sandboxing and exploit mitigations, restrict high-risk web content via filtering, and instrument endpoints for crash telemetry correlated to suspicious browsing.

References

• NVD: CVE-2026-109774 — https://nvd.nist.gov/vuln/detail/CVE-2026-109774
• Mozilla security advisories (Firefox releases): https://www.mozilla.org/security/advisories/
• Mozilla Foundation Security Advisories index: https://www.mozilla.org/en-US/security/advisories/mfsa/
• FIRST EPSS (not yet scored): https://www.first.org/epss/
• CISA Known Exploited Vulnerabilities Catalog (CVE not listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog No threat actor campaigns or exploit-in-the-wild evidence are available in the provided data.