CVE-2026-78937

Executive Summary

CVE-2026-78937 is a use-after-free (UAF) vulnerability in the Search component of Google Chrome on Android, patched in version 152.0.7977.65. A remote attacker leveraging social engineering can exploit this flaw via a crafted HTML page to potentially execute arbitrary code outside the Chrome sandbox, granting elevated privileges on the underlying Android operating system. Given the medium severity rating assigned by Chromium, the vulnerability requires significant user interaction (visiting a malicious page) but has severe post-exploitation impact if sandbox escape is achieved.

Technical Analysis

The vulnerability is classified as CWE-416 (Use After Free), a memory corruption flaw where a program continues to dereference a pointer after the memory it references has been freed. In Google Chrome's Search component on Android, a crafted HTML page can trigger this condition, causing the browser to access freed memory. The NVD description does not provide specific function names, code paths, or the exact mechanism of the UAF — insufficient technical detail is available regarding the specific object being freed or the interaction sequence that triggers the flaw.

From the vulnerability-class perspective, UAF in a browser typically occurs during DOM manipulation or Search-related operations when:

1. An object is allocated and populated with data (e.g., search results UI elements).
2. A JavaScript or DOM operation frees the object prematurely.
3. A subsequent asynchronous callback or event handler dereferences the freed pointer.

The attack surface is the Chrome browser on Android, accessed remotely via HTTP(S). The exploitation chain requires the attacker to deliver a crafted HTML page that triggers the UAF. Because the Chrome sandbox on Android restricts access to system resources, the UAF must be chained with a sandbox escape to execute code outside the sandbox. However, the NVD description states "potentially execute arbitrary code outside the sandbox," implying the UAF alone may not guarantee sandbox escape — additional vulnerabilities or weakened sandbox configurations may be required.

Exploitation Scenarios

No public PoC exists; attack chain is inferred from vulnerability class and description.

Step 1 – Reconnaissance/Phishing Delivery: The attacker crafts a malicious HTML page and hosts it on a compromised or attacker-controlled domain. Targeted victims are sent a link via SMS, email, or social media messaging apps (leveraging social engineering, consistent with the NVD description). On Android, users may be lured with themes such as "account verification," "prize notification," or "breaking news" to increase click-through rates.

Step 2 – Triggering the Use-After-Free: A victim using Chrome for Android prior to version 152.0.7977.65 opens the malicious HTML page. The page contains scripts that invoke Search-related operations designed to free a browser object while a reference to it remains active. The specific HTML constructs, JavaScript APIs, and event sequences required to trigger the UAF are not disclosed in public technical details; however, typical UAF triggers involve race conditions between synchronous page operations and asynchronous completion callbacks. The attacker controls the HTML content and can adapt to browser behavior through testing.

Step 3 – Payload Execution: Once the UAF is triggered, the freed memory region may be reallocated with attacker-controlled data. By spraying the heap with carefully crafted objects, the attacker can control the contents of the freed memory. When the dangling pointer is dereferenced, the browser's virtual function table or function pointer is invoked with attacker-controlled data, redirecting control flow. This achieves arbitrary code execution within the Chrome renderer process — still inside the sandbox.

Step 4 – Post-Exploitation: To execute code "outside the sandbox," the attacker must chain this UAF with a second vulnerability (kernel bug, Android platform flaw) or leverage known escape techniques. If successful, the attacker achieves code execution with the privileges of the Chrome sandbox on Android — typically the untrusted_app SELinux context. Post-exploitation impact includes:

• Exfiltration of browser cookies, saved passwords, and autofill data.
• Access to files readable by the Chrome app (internal storage, media files with permissions).
• Installation of persistent malware via Android package installation APIs (if permissions allow).
• Lateral movement to other apps via Android intents if the sandbox is fully escaped.

Impact Assessment

Business Impact: For enterprises with BYOD (Bring Your Own Device) policies, this vulnerability represents a remote code execution vector targeting user-controlled mobile devices. A successful exploitation could compromise corporate data accessed through Chrome on the device, including web-based email, SaaS applications, and intranet portals.

Affected Systems: Google Chrome for Android versions prior to 152.0.7977.65. The flaw does not affect Chrome on desktop platforms (Windows, macOS, Linux) as the Search component's Android-specific implementation is the vulnerable surface.

Blast Radius: The CVSS v3.1 vector reflects a network-based attack with low complexity, no privileges required, and user interaction. The scope is "Changed" (S:C) because a compromised browser process can affect components (Android OS) outside its original authorization boundary. Confidentiality, Integrity, and Availability impact are all rated High, reflecting the potential for full code execution. In practice, the severity may be lower because sandbox escapes require chaining with additional vulnerabilities, which are typically patched in Android security updates.

Detection Guidance

Sigma Rule

title: Chrome Android UAF Exploitation Attempt via Malicious HTML
id: 8f2f3d0a-6c94-4a2b-bfa5-53c8a9b2e7d1
status: experimental
description: Detects Chrome Android crashes consistent with use-after-free exploitation attempts
logsource:
    product: android
    service: logcat
detection:
    selection_crash:
        - message|contains|all:
            - 'chromium'
            - 'heap-use-after-free'
            - 'SIGSEGV'
        - message|contains|all:
            - 'libchrome'
            - 'SearchResultPage'
            - 'access violation'
    selection_origin:
        - event.type: 'crash'
        - event.category: 'process'
    condition: selection_crash and selection_origin
level: high
falsepositives:
    - Legitimate Chrome crashes from memory pressure
    - Rare browser bugs not triggered by malicious content

YARA Rule

rule CVE_2026_78937_Chrome_Android_UAF_HTML
{
    meta:
        author = "ValtersIT Threat Intel"
        description = "Detects malicious HTML content targeting Search UAF in Chrome Android"
        date = "2026-02-15"
        cve = "CVE-2026-78937"
        severity = "high"
    strings:
        $search_api = "window.search" ascii nocase
        $search_proto = "SearchProvider" ascii nocase
        $uaf_trigger = "onsearchcomplete" ascii nocase
        $dom_manip = "removeChild" ascii nocase
        $async_cb = "requestAnimationFrame" ascii nocase
        $web_rtc = "window.webkit" ascii nocase
        $html_marker = "<html" ascii nocase
    condition:
        uint16(0) == 0x3C3F or uint8(0) == 0x3C and
        filesize < 1MB and
        2 of ($search_api, $search_proto, $uaf_trigger) and
        1 of ($dom_manip, $async_cb) and
        $html_marker
}

Suricata IDS Rule

alert http any any -> any any (
    msg:"ET EXPLOIT Possible Chrome Android UAF (CVE-2026-78937) HTML Content";
    flow:established,to_server;
    content:"<html"; http_client_body;
    content:"SearchProvider"; http_client_body; distance:0;
    content:"removeChild"; http_client_body; distance:0;
    content:"onsearchcomplete"; http_client_body; distance:0;
    pcre:"/window\.[a-z]+s*\(/Ui";
    classtype:attempted-user;
    reference:url,nvd.nist.gov/vuln/detail/CVE-2026-78937;
    sid:202678937;
    rev:1;
    metadata:affected_product Android_Chrome, attack_target Client_Endpoint, deployment Perimeter, signature_severity Major;
)

Elastic Detection

sequence by host.hostname, process.entity_id with maxspan=5m
  [process where event.type == "start" and process.name == "com.google.android.chrome" and
     event.outcome != "success"]
  [file where event.type == "creation" and file.path == "/data/data/com.google.android.chrome/app_crash_recovery/*" and
     file.extension == "dmp"]

Splunk SPL Query

index=android_logs sourcetype=logcat
| search "chromium" "heap-use-after-free" OR "libchrome" "SIGSEGV"
| rex field=_raw "pid (?<pid>\d+)"
| table _time, host, pid, _raw
| eval severity = "high"
| stats count by host, pid

Wazuh OSSEC Rule

<group name="local,">
  <rule id="100789" level="10">
    <decoded_as>json</decoded_as>
    <field name="event.type">crash</field>
    <field name="process.name">com.google.android.chrome</field>
    <description>CVE-2026-78937: Chrome Android use-after-free crash detected</description>
    <group>browser_crash,chrome_android,use_after_free,</group>
    <mitre>
      <id>T1204.001</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence Note: Patch confidence is 2/4 (CLAIMED) — only a single source (NVD) claims a fix exists in Chrome 152.0.7977.65. Independent confirmation from Google's Chrome Releases blog or Chromium bug tracker has not verified this version as the fixing release.

1) Immediate Mitigations:

• Update all Android devices running Chrome to version 152.0.7977.65 or later via the Google Play Store.
• If immediate patching is not possible, enforce Managed Chrome Browser policies to disable JavaScript (via Content Settings) as a temporary measure — this will significantly reduce the attack surface but may degrade functionality.
• Block known phishing domains and implement URL filtering with real-time threat intelligence feeds.

2) Patch/Upgrade Steps:

• Navigate to Play Store → Chrome → Update. Alternatively, force-check for updates via device Settings → Apps → Chrome → App details.
• For enterprise-managed devices, use EMM/UEM consoles (e.g., Intune, Workspace ONE) to push the Chrome update or set a minimum version requirement.
• Retest all enterprise web applications in Chrome 152+ for compatibility regressions before full rollout.

3) Long-Term Hardening:

• Enforce a minimum Chrome version policy in MDM solutions to prevent devices from running outdated browsers.
• Deploy Android's "Untrusted App" SELinux policy updates from Google via monthly Android Security Patch Level (ASPL).
• Implement browser isolation (remote rendering) for high-risk web browsing on mobile devices.
• Educate users on phishing risks related to SMS and messaging app links — this vulnerability's primary vector is social engineering.
• Monitor Chromium bug tracker and Chrome Releases for independent patch confirmation and update the patch confidence rating accordingly.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-78937
2. Chrome Releases (Official Patch Notes — confirmation pending): https://chromereleases.googleblog.com
3. Chromium Bug Tracker (UAF in Search): https://bugs.chromium.org/p/chromium/issues/list?q=CVE-2026-78937
4. CWE-416 Use After Free Reference: https://cwe.mitre.org/data/definitions/416.html
5. CISA Known Exploited Vulnerabilities Catalog (CVE not currently listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Threat Actor Campaigns / Exploit-in-the-Wild: As of this reporting date, no known active exploitation campaigns have been publicly attributed to CVE-2026-78937. The CVE is not present in CISA's KEV catalog, and no exploit code or public PoC has been released. Monitoring should continue as threat actors frequently weaponize Chrome UAF vulnerabilities shortly after patch disclosure, particularly for Android targets.