CVE-2026-106205

Executive Summary

CVE-2026-106205 is a missing-authorization flaw (CWE-862) in Google Chrome on Android affecting versions prior to 155.0.8059.39. An attacker who has already compromised a renderer process can bypass the browser's site isolation boundary via a crafted HTML page, allowing cross-origin data access or further privilege escalation within the multi-process architecture. The Chromium project rates the issue as Medium severity. No public proof-of-concept, Nuclei template, or exploit code is currently available, and no patch evidence has been confirmed by tracked sources.

Technical Analysis

Chrome's security model assumes that each renderer process is sandboxed and that origin isolation prevents a compromised renderer from reading data belonging to other origins. Site isolation enforces this by assigning distinct processes per site and by brokering all cross-origin access through the browser process with strict authorization checks.

CVE-2026-106205 is classified as CWE-862: Missing Authorization. In this context, a missing authorization check means that an internal operation that should verify the caller's identity, origin, or permission context does not perform that verification. Because the flaw exists in the "Passwords" component (per the NVD description), the affected surface is the credential-related IPC or service interface exposed to renderer processes. A renderer that successfully triggers the unguarded code path can perform an operation — presumably a password-related action — that should have required authorization.

The attack requires the threat model that Chrome explicitly treats as in-scope: a renderer process has already been compromised (for example by a separate memory corruption or logic bug). The NVD description states the flaw is reachable "via a crafted HTML page," meaning the trigger is delivered through normal web content rendering rather than requiring local access. The impact is stated as a bypass of site isolation — the browser-level barrier that separates origins and protects credential material from cross-origin speculation or side-channel reads.

Two constraints should be noted. First, no technical detail beyond the CNA description is available; function names, IPC message identifiers, and exact code paths are not disclosed and are deliberately not invented here. Second, the prerequisite of a compromised renderer raises the exploitation bar: a standalone crafted HTML page is not asserted to be sufficient — an initial renderer compromise is a precondition.

Exploitation Scenarios

No public PoC is available; the chain below is inferred strictly from the vulnerability class and the NVD description.

1. Reconnaissance / target identification. The attacker identifies users running Chrome on Android below 155.0.8059.39. Because no version-disclosure-specific dork exists, identification is generic: fingerprinting Chrome on Android via user-agent, feature detection, or serving content to a broad audience and filtering by capability.

2. Initial renderer compromise. The attacker must first obtain code execution inside a Chrome renderer process. This is a separate vulnerability (e.g., a memory-corruption issue) and is a hard prerequisite. Without it, CVE-2026-106205 is not reachable, per the stated threat model.

3. Triggering the missing-authorization flaw. The attacker delivers a crafted HTML page. When the compromised renderer processes this page, it reaches a password-component operation that lacks an authorization check. Because the check is absent, the renderer is not validated for the expected origin or permission scope, and the operation proceeds.

4. Site isolation bypass. The unguarded operation crosses the process/origin boundary that site isolation is designed to enforce. The renderer can then access data or invoke behavior belonging to a different origin than the page it is rendering — the defining consequence stated in the description.

5. Post-exploitation impact. The concrete effect is credential exposure (Passwords component) and loss of the origin boundary. In the Chrome threat model, a site isolation bypass is treated as high impact because it converts a contained renderer compromise into cross-origin data access and materially expands what an attacker can read or manipulate.

Because the description does not enumerate affected data structures, IPC interfaces, or the specific authorization predicate, no further granularity can be asserted without fabrication.

Impact Assessment

• Confidentiality (High): The Passwords component and cross-origin data become readable, consistent with a site isolation bypass.
• Integrity (High): The integrity of origin-separated state is undermined; an attacker with renderer control can affect decisions that assume isolation.
• Availability (None asserted): The description does not indicate a denial-of-service condition.
• Scope (Changed): The vulnerable component's authorization boundary is crossed — a renderer compromise escalates to impact beyond the renderer's own security context.
• Privileges Required (None): Remote delivery via crafted HTML.
• User Interaction (Required): The victim must load the crafted page.
• Attack Complexity (High): Requires a pre-existing renderer compromise plus a user action, not a single-step remote exploit.

Business impact concentrates on credential theft for enterprise-managed Android fleets where Chrome is the default browser and password autofill/sync is enabled. Blast radius is limited by the renderer-compromise prerequisite; the flaw is a privilege-escalation and isolation-bypass primitive, not an unauthenticated remote code execution bug. Chrome on Android is the dominant mobile browser, so a reliable chain would have broad reach. CVSS-specific vendor scoring is not published (N/A), so the vector above is an analytical estimate reflecting the changed-scope, interaction-required nature of the flaw.

Detection Guidance

Detection is constrained: no exploit artifacts or PoC signatures exist, and the trigger is a crafted HTML page with no published indicator. The rules below target the class of behavior (compromised-renderer activity, credential-component abuse, anomalous multi-process behavior) rather than a specific byte pattern, and should be tuned before deployment.

Sigma Rule

title: Chrome on Android - Suspected Site Isolation Bypass / Renderer Authorization Failure (CVE-2026-106205)
id: 8f3c1d2e-4a6b-4c9d-9e10-7a2b3c4d5e6f
status: experimental
description: Detects process and crash telemetry consistent with a compromised Chrome renderer on Android triggering a missing-authorization condition in the password component. Class-level detection; no public PoC exists.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-106205
author: valtersit.com
date: 2026/01/01
tags:
  - attack.t1190
logsource:
  product: android
  service: chromium
detection:
  selection_proc:
    Image|endswith:
      - 'com.android.chrome'
      - 'chrome'
  selection_behavior:
    - Message|contains: 'renderer'
    - Message|contains: 'site_isolation'
    - Message|contains: 'password_manager'
    - Message|contains: 'crash'
  condition: selection_proc and selection_behavior
fields:
  - Message
  - Image
  - User
falsepositives:
  - Legitimate renderer crashes during normal navigation
  - Chrome updates and restarts
level: medium

YARA Rule

rule CVE_2026_106205_Chrome_Android_Renderer_Authz_Bypass
{
    meta:
        author = "valtersit.com"
        description = "Class-level detection for crafted HTML targeting Chrome on Android site isolation bypass (CVE-2026-106205)"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-106205"
        date = "2026-01-01"
        severity = "medium"

    strings:
        $s1 = "site isolation" nocase
        $s2 = "password_manager" nocase
        $s3 = "about:blank" nocase
        $r1 = /<iframe[^>]{0,256}srcdoc/i
        $r2 = /document\.domain\s*=/i

    condition:
        uint32be(0) == 0x3C21444F // "<!DO"
        and filesize < 2MB
        and 2 of ($s*) 
        or 1 of ($r*)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-106205 - Chrome on Android crafted HTML site isolation bypass attempt"; flow:established,to_client; http.user_agent; content:"Android"; http.user_agent; content:"Chrome/"; content:"<iframe"; http.response_body; content:"srcdoc"; http.response_body; threshold:type limit,track by_src,count 10,seconds 60; classtype:attempted-user; reference:cve,2026-106205; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-106205; sid:2026106205; rev:1;)

Elastic Detection

process where event.type == "start" and process.name : ("com.android.chrome", "chrome") and
  process.args : ("*renderer*", "*--type=renderer*") and
  not process.parent.name : "zygote"

Splunk SPL Query

index=android_chrome sourcetype=chromium:log
| search ("renderer" AND ("site_isolation" OR "password_manager" OR "authorization"))
| stats count min(_time) as first_seen max(_time) as last_seen by host, process, Message
| where count > 0
| convert ctime(first_seen) ctime(last_seen)

Wazuh OSSEC Rule

<group name="chrome,cve-2026-106205,">
  <rule id="100620" level="10">
    <decoded_as>json</decoded_as>
    <field name="Image">\.*com\.android\.chrome$|\.*chrome$</field>
    <match>renderer|site_isolation|password_manager|authorization</match>
    <description>CVE-2026-106205: Suspected Chrome on Android renderer authorization failure / site isolation bypass</description>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate mitigations

   • Update Chrome on Android to 155.0.8059.39 or later as the primary action, per the version stated in the NVD description. Verify the installed build under Settings → About Chrome; because tracked sources show no verified advisory, independently confirm the fixed build against Google's official Chrome Android release notes before relying on it.
   • Enforce strict site isolation where configurable, and treat any renderer crash followed by anomalous credential-component activity as a potential exploitation signal.
   • Where feasible, reduce renderer compromise surface: keep the browser current, disable unused features, and avoid browsing untrusted content on unmanaged Android devices.
   • For managed fleets, use MDM/Play policy to force minimum browser versions and to block sideloaded browser builds that may lag on patches.

2. Patch / upgrade steps

   • Stage and push Chrome Android 155.0.8059.39+ via Play Store managed updates or MDM enforcement.
   • Maintain an inventory of devices below the fixed build; re-scan after each update cycle.
   • Because patch verification confidence is 0/4, do not mark remediation complete until the fixed build is confirmed present on endpoints.

3. Long-term hardening

   • Enforce automatic browser updates and minimum-version baselines across Android endpoints.
   • Limit credential exposure: pair browser password storage with platform keystore protections and enterprise credential managers rather than relying on browser autofill alone.
   • Monitor for renderer-compromise precursors (memory-corruption exploitation) since this flaw is only reachable after an initial renderer compromise.
   • Track Chromium security releases and treat site isolation bypasses as high-priority even when rated Medium, given their role in exploit chains.

References

• NVD — CVE-2026-106205: https://nvd.nist.gov/vuln/detail/CVE-2026-106205
• CWE-862 — Missing Authorization: https://cwe.mitre.org/data/definitions/862.html
• Google Chrome Releases (Android, stable channel): https://chromereleases.googleblog.com/
• Chromium Site Isolation design documentation: https://www.chromium.org/Home/chromium-security/site-isolation/
• CISA KEV catalog (no entry for CVE-2026-106205 as of this report): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Note on threat actor activity: No exploit-in-the-wild evidence, no CISA KEV listing, no public PoC, and no known campaign associations were identified for CVE-2026-106205 in the data provided. The prerequisite of a compromised renderer makes standalone mass exploitation unlikely without a paired initial-access vulnerability.