CVE-2026-106213

Executive Summary

CVE-2026-106213 is a race condition vulnerability in the WebAudio component of Google Chrome versions prior to 155.0.8059.39. A remote attacker can exploit this flaw to leak cross-origin data by convincing a victim to load a crafted HTML page, requiring user interaction. The vulnerability carries a Chromium security severity of Medium and a CVSS v3.1 base score of 4.3, with the primary impact being confidentiality loss (limited) and no impact to integrity or availability.

Technical Analysis

The vulnerability resides within Chrome's WebAudio implementation. WebAudio is the browser API that enables processing and synthesizing audio in web applications, operating largely through the audio rendering thread and associated processing graph. CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization, commonly known as race condition) indicates that the flaw stems from a timing-dependent synchronization issue between concurrent execution contexts within WebAudio.

In a browser engine, WebAudio runs on a dedicated real-time audio thread that must coordinate with the main thread, the JavaScript execution context, and IPC boundaries. A race condition in this context typically means that a state transition, resource access, or ownership check is performed without adequate locking or ordering guarantees. When two execution paths interleave in an unexpected sequence, the intended security boundary — in this case, the cross-origin isolation of data accessible to WebAudio — can be bypassed or observed transiently.

The specific consequence described is cross-origin data leakage. Cross-origin policy is a foundational browser security control that prevents a document loaded from one origin from reading data belonging to another origin. The race condition allows a crafted HTML page — controlled by the attacker — to create a timing window during which WebAudio-related processing exposes data that should remain isolated to a different origin. Because this is a race, exploitation is inherently probabilistic: the attacker must trigger the concurrent condition and win the timing window, potentially requiring many attempts.

The attack surface is remote and network-accessible (AV:N), requires no privileges (PR:N), and demands user interaction (UI:R) — the victim must visit the attacker's crafted page. The confidentiality impact is rated Low (C:L), reflecting that leakage is limited in scope or volume rather than a full compromise of arbitrary cross-origin memory. Notably, the NVD description does not disclose the specific functions, interfaces, or data structures involved, nor the precise synchronization primitive that failed. Accordingly, this report does not speculate on internal method names or code paths. The description is sufficient to classify the bug as a concurrency/synchronization defect producing an information disclosure, but insufficient to reconstruct the exact exploitation primitive at a code level.

Chromium's security severity rating for this issue is Medium, which aligns with the CVSS assessment: a meaningful but non-critical information disclosure that is not remotely triggerable without a victim action and does not yield code execution, privilege escalation, or persistence.

Exploitation Scenarios

No public proof-of-concept, Nuclei template, or exploit code is available for CVE-2026-106213, and no exploitation has been observed in the wild as tracked by CISA KEV. The attack chain below is therefore inferred at the vulnerability-class level, strictly from the NVD description. Specific function names, object names, or parameters are not disclosed in the source data and are not invented here.

1. Reconnaissance / Target Identification. The attacker identifies targets running Google Chrome versions earlier than 155.0.8059.39. Because the flaw is in a broadly deployed browser, any user on an unpatched Chrome build is potentially in scope. The attacker needs no knowledge of the victim's environment beyond the ability to deliver web content.

2. Triggering the Flaw Class. The attacker hosts or injects a crafted HTML page. The page leverages WebAudio functionality in a manner that induces concurrent execution relevant to the race condition — that is, it drives the browser to interleave operations in a way that violates the intended synchronization on a shared WebAudio resource. The precise construction is not documented in the available intelligence; the defining characteristic is a timing-dependent maneuver that opens a window of inconsistent state.

3. Payload / Execution. Delivery is via a victim loading the crafted page (UI:R), for example by visiting a malicious site or a page with attacker-injected content. Upon load, the page executes WebAudio operations designed to win the race. When the timing window is hit, cross-origin data becomes observable to the page.

4. Post-Exploitation Impact. The attacker obtains limited cross-origin data that should have been inaccessible. This constitutes an information disclosure that could contribute to further attacks (e.g., inferring cross-origin content or state), but in itself does not provide code execution, privilege escalation, or persistence. Reliability depends on winning a race, so repeated attempts or favorable timing may be required.

It is important to state explicitly that no public exploit chain has been demonstrated. This section describes the plausible mechanism consistent with a WebAudio race condition leading to cross-origin leakage, not a verified exploit.

Impact Assessment

CVE-2026-106213 has a CVSS v3.1 base score of 4.3 (Medium). The subscores are: Attack Vector Network (AV:N), Attack Complexity Low (AC:L), Privileges Required None (PR:N), User Interaction Required (UI:R), Scope Unchanged (S:U), Confidentiality Low (C:L), Integrity None (I:N), Availability None (A:N).

Business impact centers on confidentiality. An attacker able to leak cross-origin data from a victim's browser session can potentially access information that same-origin policy is designed to protect, which may include session-related or content-derived data depending on what WebAudio surfaces. The Low confidentiality rating indicates the leakage is bounded rather than a wholesale read of arbitrary memory.

The blast radius is broad in terms of potential population — every user of an unpatched Chrome build below 155.0.8059.39 — but shallow in terms of per-victim impact, given Low confidentiality and no integrity or availability effects. There is no evidence of active exploitation, no KEV listing, and no public PoC. EPSS has not yet been scored by FIRST.org; no EPSS value should be assumed. The combination of Low severity, user-interaction requirement, and absence of exploitation artifacts suggests prioritized patching rather than emergency response.

Detection Guidance

Sigma Rule

title: Chrome WebAudio Race Condition Cross-Origin Data Leak Attempt (CVE-2026-106213)
id: 3f9c2b7a-1d4e-4a8b-9c2f-7e6d5a4b3c21
status: experimental
description: Detects anomalous WebAudio usage consistent with race-condition exploitation attempts in Chrome.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-106213
author: valtersit.com
date: 2026/01/01
logsource:
  category: process_creation
  product: windows
detection:
  selection_img:
    Image|endswith:
      - '\chrome.exe'
      - '\chromium.exe'
  selection_cmd:
    CommandLine|contains:
      - '--disable-web-security'
      - '--disable-site-isolation-trials'
  condition: selection_img and selection_cmd
falsepositives:
  - Developer testing environments
level: low

YARA Rule

rule CVE_2026_106213_WebAudio_Race_XOrigin_Leak
{
    meta:
        description = "Detects HTML/JS content attempting WebAudio race-condition exploitation against Chrome"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-106213"
        date = "2026-01-01"
        severity = "medium"
    strings:
        $a = "AudioContext" ascii nocase
        $b = "webkitAudioContext" ascii nocase
        $c = "createScriptProcessor" ascii nocase
        $d = "OfflineAudioContext" ascii nocase
        $e = "postMessage" ascii nocase
    condition:
        uint32(0) != 0x504b0304 and
        filesize < 2MB and
        (2 of ($a, $b, $c, $d)) and $e
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-106213 Chrome WebAudio Race Condition Cross-Origin Leak Attempt"; flow:established,to_client; content:"AudioContext"; nocase; http_server_body; content:"OfflineAudioContext"; nocase; http_server_body; distance:0; content:"postMessage"; nocase; http_server_body; distance:0; classtype:attempted-recon; reference:cve,2026-106213; sid:2026106213; rev:1;)

Elastic Detection

process where process.name in ("chrome.exe", "chromium.exe") and
  process.command_line : ("*--disable-web-security*" or "*--disable-site-isolation-trials*")

Splunk SPL Query

index=web sourcetype=proxy OR sourcetype=pan:traffic
| search http_content="*AudioContext*" AND http_content="*postMessage*"
| where http_content LIKE "%OfflineAudioContext%" OR http_content LIKE "%createScriptProcessor%"
| stats count min(_time) as first_seen max(_time) as last_seen by src_ip, dest_host, uri
| where count > 1
| convert ctime(first_seen) ctime(last_seen)

Wazuh OSSEC Rule

<group name="web,chrome,cve_2026_106213,">
  <rule id="2026106" level="6">
    <decoded_as>json</decoded_as>
    <field name="process.name">chrome.exe|chromium.exe</field>
    <match>--disable-web-security|--disable-site-isolation-trials</match>
    <description>CVE-2026-106213: Chrome launched with security-disabling flags, potential WebAudio race exploitation testing</description>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). No vendor fix reference, workaround, or advisory has been confirmed in tracked sources. The only version reference available is from the NVD description, which states the flaw affects Chrome prior to 155.0.8059.39. Treat patch availability as unverified until a vendor advisory is confirmed.

1. Immediate Mitigations.

• Update Google Chrome to version 155.0.8059.39 or later if such a build is available from the vendor; verify via the vendor's official release channels before relying on it.
• Enforce browser auto-update policies across the fleet so managed devices receive current builds without manual intervention.
• Restrict browsing to trusted origins where feasible, and deploy web content filtering to reduce exposure to untrusted HTML.
• Enable site isolation and avoid disabling web security features; do not launch Chrome with flags that weaken cross-origin protections.
• Consider temporarily steering high-risk users to an alternative, fully patched browser if an update is not yet deployable.

2. Patch / Upgrade Steps.

• Confirm the installed Chrome version (e.g., via the browser's version page or endpoint inventory tools).
• Where a fixed build is published by the vendor, stage and deploy it through your software distribution pipeline and verify the resulting version.
• Monitor the vendor's security release notes for the advisory mapped to this CVE to confirm exact fixed build and any backports.

3. Long-Term Hardening.

• Maintain continuous browser version monitoring and alerting for outdated builds.
• Adopt a rapid patch cadence for browsers given their broad attack surface.
• Keep site isolation and origin isolation features enabled and audited.
• Use enterprise browser management to enforce policy and prevent users from disabling security controls.
• Subscribe to vendor security bulletins and CVE feeds to catch advisories promptly.

References

• NVD — CVE-2026-106213: https://nvd.nist.gov/vuln/detail/CVE-2026-106213
• MITRE CWE-362 (Race Condition): https://cwe.mitre.org/data/definitions/362.html
• FIRST EPSS (not yet scored for this CVE): https://www.first.org/epss/
• CISA Known Exploited Vulnerabilities Catalog (CVE not listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog
• Google Chrome release notes / security advisories (verify latest fixed build and advisory mapping): https://chromereleases.googleblog.com/

No known threat actor campaigns or exploit-in-the-wild evidence have been identified for CVE-2026-106213. The vulnerability is not listed in CISA KEV, no public proof-of-concept or exploit code is available, and EPSS has not yet assigned a score.