CVE-2026-78964 Overview
CVE-2026-78964 is a use-after-free vulnerability in the Sync component of Google Chrome on iOS. Versions prior to 152.0.7977.65 are affected. A remote attacker can trigger the flaw with a crafted HTML page and potentially execute arbitrary code outside the browser sandbox. The weakness is classified under CWE-416. Exploitation requires user interaction such as visiting an attacker-controlled page. Google's Chromium security team rated the internal severity as Low, but the assigned NVD score reflects a broader impact including scope change and full loss of confidentiality, integrity, and availability.
Critical Impact
Successful exploitation permits arbitrary code execution outside the Chrome sandbox on iOS through a single crafted web page.
Affected Products
- Google Chrome on iOS prior to 152.0.7977.65
- Apple iPhone OS (as host platform for the affected Chrome build)
- Any Chromium-derived iOS build embedding the vulnerable Sync component
Discovery Timeline
- 2026-08-25 - CVE-2026-78964 published to the National Vulnerability Database
- 2026-08-27 - Last updated in NVD database
Technical Details for CVE-2026-78964
Vulnerability Analysis
The flaw resides in Chrome's Sync subsystem, which coordinates user data such as bookmarks, tabs, and settings across devices. A use-after-free condition occurs when the component references heap memory after it has been released. An attacker who serves a crafted HTML page can drive the Sync code path into this dangling reference state during normal browsing.
Once the freed object is reallocated with attacker-controlled data, code execution can be redirected. The advisory notes the impact extends outside the browser sandbox, indicating the primitive can be chained to break iOS process isolation for Chrome. The vulnerability requires user interaction, consistent with the drive-by-download exploitation model common to browser bugs.
Root Cause
The root cause is improper lifetime management of an object in the Sync component. Chromium's Sync engine maintains references to model objects across asynchronous callbacks. When an object is destroyed while a pending callback still holds a raw pointer, dereferencing that pointer produces the use-after-free. The Chromium tracker entry Issue #539341100 contains the restricted technical details.
Attack Vector
Exploitation is network-based. The attacker hosts a malicious HTML page and lures a signed-in Chrome iOS user to visit it. JavaScript on the page manipulates Sync state or triggers Sync operations that provoke the freed-object access. Combined with a heap grooming primitive, this yields code execution beyond the renderer sandbox.
No public proof-of-concept exploit is available. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.
No verified exploit code is publicly available for CVE-2026-78964.
Refer to the Chromium issue tracker for restricted technical details:
https://issues.chromium.org/issues/539341100
Detection Methods for CVE-2026-78964
Indicators of Compromise
- Unexpected Chrome renderer or GPU process crashes on iOS coinciding with visits to unfamiliar domains
- Anomalous Sync traffic patterns to clients4.google.com or sync.chrome.google.com from managed iOS fleets
- Web navigation logs showing users on Chrome iOS builds earlier than 152.0.7977.65 reaching newly registered or low-reputation domains
Detection Strategies
- Inventory Chrome iOS versions across MDM-enrolled devices and flag any build earlier than 152.0.7977.65
- Correlate browser crash telemetry with proxy logs to identify pages that trigger repeated Sync-related faults
- Apply threat intelligence feeds for domains and URLs associated with browser exploit kits targeting Chromium use-after-free bugs
Monitoring Recommendations
- Ingest MDM and browser telemetry into a centralized analytics platform to track Chrome version drift on iOS
- Alert on outbound connections from Chrome iOS clients to domains scoring low on URL reputation services
- Monitor for privilege escalation or unexpected child process activity on managed iOS devices where feasible under Apple's platform constraints
How to Mitigate CVE-2026-78964
Immediate Actions Required
- Update Google Chrome on iOS to version 152.0.7977.65 or later through the Apple App Store
- Push a mandatory update policy through mobile device management to enforce the fix on enrolled devices
- Communicate the risk to end users and instruct them to restart Chrome after the update to complete the patch
Patch Information
Google released the fix in the Chrome stable channel update documented in the Google Chrome Stable Update advisory. Installing Chrome 152.0.7977.65 or a later build from the App Store remediates the vulnerability. The underlying Chromium fix is tracked in Chromium Issue #539341100.
Workarounds
- Sign out of Chrome Sync on iOS until the update is installed to reduce exposure of the vulnerable code path
- Restrict browsing on unpatched devices to a trusted allowlist through MDM web content filtering
- Use an alternate browser on iOS for untrusted browsing sessions until the Chrome update is deployed
# Verify installed Chrome iOS version via MDM query (example: Jamf Pro)
# Target application bundle identifier: com.google.chrome.ios
# Required minimum version: 152.0.7977.65
jamf policy -event enforce-chrome-ios-update
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
