CVE-2026-109743

Executive Summary

CVE-2026-109743 is a privilege escalation vulnerability affecting the Panning and Zooming component of Mozilla Firefox. This flaw allows an attacker to escalate privileges beyond their authorized level within the browser context. The vulnerability was addressed in Firefox 158 and Firefox ESR 153.5; all earlier versions of these release trains remain vulnerable.

Technical Analysis

The vulnerability resides in Firefox's Panning and Zooming component, which is the subsystem responsible for handling user-initiated scroll, pan, and pinch-zoom gestures and their corresponding content transformations. Per the NVD description, the flaw is classified as a privilege escalation, meaning an actor operating at one privilege level can obtain capabilities or access rights belonging to a higher level.

Because the NVD description, CNA title, CWE, and CVSS vector are not provided with additional technical granularity, the precise root cause — for example, whether this arises from improper trust-boundary enforcement between web content and a privileged (chrome/parent-process) context, a use-after-free condition reached through gesture handling, or a state-confusion issue in gesture-to-content mapping — cannot be determined from the available data. Analysts should treat the following as class-level characterization rather than confirmed implementation detail.

Privilege escalation in a browser typically involves crossing either:

1. A process boundary, where an unprivileged content (renderer) process gains capabilities held by the privileged parent/browser process, or
2. A same-origin/privileged-UI boundary, where a web-exposed surface triggers privileged functionality that should be gated behind user or system consent.

The Panning and Zooming component is directly reachable from untrusted web content through ordinary user interaction (scrolling, pinch-zoom, gesture events) and through synthetic events dispatched by script. This reachability is significant: it means the vulnerable attack surface is exposed to any web page the user visits, requiring no special network position or authentication. The interaction requirement (a gesture or its synthetic equivalent) is consistent with a UI:R style vector, reduced only by the attacker's ability to induce the interaction.

The public record contains no root-cause disclosure, no crash signature, no affected code identifier, and no CWE assignment. No memory-safety or logic-error classification can be asserted from the available data.

Exploitation Scenarios

No public PoC is available; the attack chain below is inferred strictly from the vulnerability class (privilege escalation in a browser gesture/zoom component) and the NVD description. No specific function names, file paths, APIs, or endpoints are asserted because none are present in the source data.

1. Reconnaissance / target identification: An attacker identifies Firefox installations below version 158 (or ESR below 153.5). This can be done passively — for example, through browser-fingerprinting techniques that infer the engine and version from feature support or via user-agent disclosure. No Shodan-exposed service is strictly required, since the target is the client browser; web-based delivery is the primary vector.

2. Triggering the flaw class: The attacker delivers a web page (or injected content on a compromised/legitimate site) that induces the vulnerable panning and zooming code path. Based on the vulnerability class, the trigger would involve bringing the Panning/Zooming component into an unexpected state — for example, by manipulating gesture or zoom state transitions faster than the component can safely reconcile them, or by combining synthetic gesture events with a privileged boundary crossing. The exact sequence is unknown from public data.

3. Payload / execution at class level: Because the flaw is a privilege escalation, the objective of the trigger is to cause the component to perform an action — or to enter a state — that should only be reachable from a more privileged context. Depending on the root cause (process-boundary confusion versus same-process privilege confusion), the outcome could range from elevated same-process capabilities to crossing into the browser/parent process. No specific payload structure can be described without root-cause data.

4. Post-exploitation impact: Successful escalation could grant an attacker capabilities normally reserved for the browser's privileged context, potentially enabling broader access to the user's session, credentials, or local resources than the compromised web content would otherwise permit. The exact blast radius is bounded by the component's privilege level and remains unconfirmed.

Impact Assessment

CVSS base score is not available from the provided data (N/A), and no official vector was published, so subscore values cannot be reported as authoritative. Based on the vulnerability class, an analyst-assessed worst-case impact configuration is:

• Confidentiality: High
• Integrity: High
• Availability: High
• Attack Vector: Network (browser-delivered content)
• Attack Complexity: Low to Medium (state manipulation may require precise timing)
• Privileges Required: None
• User Interaction: Required (gesture/zoom interaction, potentially synthetic)
• Scope: Unchanged (assuming same-process or same-trust-domain escalation)

Affected systems: consumer and enterprise endpoints running Mozilla Firefox below 158 and Firefox ESR below 153.5. Blast radius scales with the size of the unpatched Firefox population — commonly all unmanaged and non-auto-updating endpoints. Because the attack does not require network position or credentials, any exposed user session is a candidate target. Enterprise risk is elevated where Firefox is used to access SSO portals, webmail, or administrative consoles, since escalation could expose session tokens or privileged browser-level capabilities.

Detection Guidance

The following rules are best-effort detections keyed to the vulnerability class (browser privilege escalation via gesture/zoom abuse) and to the patched versions. They should be tuned in a lab before production deployment. Given the absence of specific function names or network indicators, detections focus on anomalous gesture/zoom event patterns, unexpected privilege transitions, and version-based exposure.

Sigma Rule

title: Firefox Privilege Escalation via Panning and Zooming Component - Suspicious Child Process
id: 8d2f4a11-6c3b-4f9e-a1d2-7b5c9e0f3a62
status: experimental
description: Detects unusual child process spawning from Firefox consistent with privilege escalation post-exploitation (CVE-2026-109743).
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-109743
author: Threat Intelligence Team
date: 2026/01/01
logsource:
  category: process_creation
  product: windows
detection:
  selection_parent:
    ParentImage|endswith:
      - '\firefox.exe'
      - '/firefox'
  selection_child:
    Image|endswith:
      - '\cmd.exe'
      - '\powershell.exe'
      - '\wscript.exe'
      - '\cscript.exe'
      - '\mshta.exe'
      - '\rundll32.exe'
      - '/sh'
      - '/bash'
  condition: selection_parent and selection_child
falsepositives:
  - Legitimate browser helper processes or enterprise tooling
level: high

YARA Rule

rule CVE_2026_109743_Firefox_PrivEsc_Gesture_Zoom
{
    meta:
        description = "Heuristic detection for exploit artifacts targeting the Firefox Panning and Zooming privilege escalation (CVE-2026-109743)"
        author = "Threat Intelligence Team"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-109743"
        date = "2026-01-01"
        severity = "high"

    strings:
        $gesture1 = "PanningAndZooming" ascii wide nocase
        $gesture2 = "panning_zooming" ascii wide nocase
        $gesture3 = "PanZoomController" ascii wide nocase
        $esc = "privesc" ascii wide nocase
        $esc2 = "elevate" ascii wide nocase
        $js1 = "dispatchEvent" ascii wide nocase
        $js2 = "wheel" ascii wide nocase
        $js3 = "gesture" ascii wide nocase

    condition:
        uint16(0) == 0x5A4D or uint32(0) == 0x464C457F or filesize < 10MB
        and (
            any of ($gesture*)
            or (2 of ($esc*) and 1 of ($js*))
        )
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-109743 Firefox Panning/Zooming Privilege Escalation Attempt"; flow:established,to_client; http.user_agent; content:"Firefox"; nocase; content:!"158"; content:!"153.5"; pcre:"/(?:Mozilla\/5\.0.*Firefox\/(?:1[0-5][0-9]|15[0-7]))/"; classtype:attempted-user; sid:2026109743; rev:1; reference:cve,2026-109743; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-109743;)

Elastic Detection

process where host.os.type == "windows" and
  process.parent.name == "firefox.exe" and
  process.name in ("cmd.exe", "powershell.exe", "wscript.exe", "cscript.exe", "mshta.exe", "rundll32.exe")

Splunk SPL Query

index=endpoint (EventCode=4688 OR source="*Sysmon*" EventCode=1)
| search ParentImage="*\\firefox.exe" AND Image IN ("*\\cmd.exe","*\\powershell.exe","*\\wscript.exe","*\\cscript.exe","*\\mshta.exe","*\\rundll32.exe")
| stats count min(_time) as first_seen max(_time) as last_seen by host, ParentImage, Image, CommandLine
| convert ctime(first_seen) ctime(last_seen)
| sort - count

Wazuh OSSEC Rule

<group name="firefox,cve_2026_109743,">
  <rule id="1097430" level="12">
    <if_sid>60000</if_sid>
    <field name="win.eventdata.parentImage">firefox\.exe$</field>
    <field name="win.eventdata.image">(?i)(cmd|powershell|wscript|cscript|mshta|rundll32)\.exe$</field>
    <description>CVE-2026-109743: Suspicious child process spawned by Firefox (possible privilege escalation)</description>
    <mitre>
      <id>T1068</id>
    </mitre>
    <group>privilege_escalation,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). The NVD description states the issue was fixed in Firefox 158 and Firefox ESR 153.5; however, no vendor advisory, patch commit, or MDN/Release Notes reference was provided in the source data, so the fix reference cannot be independently confirmed here.

1. Immediate mitigations:

   • Update Firefox to 158 or later, and Firefox ESR to 153.5 or later, as reflected in the NVD description. These are the versions stated to contain the fix.
   • Where immediate update is not possible, restrict general-purpose web browsing from unpatched Firefox profiles, particularly for users accessing privileged web applications (SSO, webmail, admin consoles). Migrate such access to a patched browser.
   • Enforce browser auto-update policy via enterprise management (e.g., DisableAppUpdate=false, or equivalent GPO/configuration policy) to eliminate the unpatched window on managed endpoints.
   • Reduce the attack surface by enabling site isolation and hardening content settings where operationally feasible.

2. Patch/upgrade steps:

   • Verify installed version against 158 (release) or 153.5 (ESR). Unpatched versions are any release below the stated fix versions.
   • Deploy the fixed build through your standard patch pipeline; validate the reported version in the browser's about dialog or via endpoint inventory.
   • Confirm ESR channels receive 153.5 independently of the main release train.

3. Long-term hardening:

   • Maintain an authoritative software inventory with browser version tracking and drift alerting.
   • Enforce a short patch SLA for browser software, prioritizing endpoints that access privileged applications.
   • Deploy the detection rules above to monitor for post-exploitation behavior associated with browser privilege escalation (unexpected child processes, credential-store access).
   • Consider application isolation/containerization for high-risk browsing.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-109743
• Mozilla Security Advisories: https://www.mozilla.org/en-US/security/advisories/
• Mozilla Firefox Release Notes: https://www.mozilla.org/en-US/firefox/releases/
• Mozilla Firefox ESR Release Notes: https://www.mozilla.org/en-US/firefox/enterprise/
• CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE-2026-109743 not listed as of this report)

No threat actor campaigns or exploit-in-the-wild evidence were provided in the source data. CISA KEV status is NO. No public PoC, Nuclei template, or exploit code was available at the time of writing.