CVE-2026-17858 Overview
CVE-2026-17858 is an uninitialized memory use vulnerability in the Web Neural Network API (WebNN) implementation in Google Chrome on Windows. Versions prior to 151.0.7922.72 are affected. A remote attacker can leak cross-origin data by serving a crafted HTML page to a targeted user. Chromium security engineers rated the flaw Medium severity. The weakness is tracked as CWE-457: Use of Uninitialized Variable and impacts the confidentiality of data isolated by the same-origin policy.
Critical Impact
Successful exploitation allows a remote attacker to read cross-origin data from a victim's browser session by luring them to a malicious page.
Affected Products
- Google Chrome for Windows prior to 151.0.7922.72
- WebNN API component in the Chromium rendering engine
- Chromium-based browsers on Windows that ship the affected WebNN implementation
Discovery Timeline
- 2026-07-30 - CVE-2026-17858 published to NVD
- 2026-07-30 - Last updated in NVD database
- Fix shipped via the Chrome Stable Channel Update for Desktop and tracked in Chromium Issue #520191468
Technical Details for CVE-2026-17858
Vulnerability Analysis
The defect resides in the WebNN implementation, which exposes hardware-accelerated machine learning primitives to JavaScript running in the browser. Under a specific code path, WebNN consumes a memory buffer or variable before it has been initialized. The uninitialized region retains residual data from prior allocations. When that data is returned to script or reflected into observable computation results, an attacker can reconstruct cross-origin content.
Because the leak surfaces through a standard web API, no additional privilege, user gesture beyond page navigation, or local access is required. The attack executes entirely in the renderer sandbox but crosses the same-origin trust boundary, defeating a core browser security guarantee.
Root Cause
The root cause is classified as CWE-457: Use of Uninitialized Variable. WebNN allocates buffers to hold tensor or intermediate operator state, then reads from those buffers without a preceding write. On Windows, the affected code path returns memory whose contents depend on prior heap or arena usage, which may include data from other origins loaded in the same process.
Attack Vector
An attacker hosts a crafted HTML page that invokes WebNN operations designed to trigger the uninitialized read. When a victim visits the page, the returned tensor values expose bytes from memory that should be inaccessible to the attacker's origin. The attacker then serializes those bytes through standard JavaScript channels to exfiltrate cross-origin content such as authenticated resources previously loaded in the same renderer process.
Google has not published proof-of-concept code. Technical details are restricted through the Chromium issue tracker entry until a majority of users have updated.
Detection Methods for CVE-2026-17858
Indicators of Compromise
- Chrome browser processes on Windows endpoints running versions earlier than 151.0.7922.72
- Outbound connections from browser sessions to attacker-controlled domains immediately after loading pages that invoke WebNN APIs
- Unexpected JavaScript workloads referencing navigator.ml or WebNN builder methods on untrusted origins
Detection Strategies
- Inventory installed Chrome versions across managed endpoints and flag any build below 151.0.7922.72.
- Monitor endpoint telemetry for chrome.exe child processes loading unusual content from unclassified or newly registered domains.
- Correlate browser navigation logs with proxy or DNS telemetry to identify visits to pages that instantiate WebNN contexts from low-reputation origins.
Monitoring Recommendations
- Ingest browser version telemetry into your SIEM and alert on out-of-date Chrome installations.
- Track Chromium stable channel advisories and map new CVEs to endpoint patch state.
- Review web proxy logs for anomalous data volumes exiting user browsing sessions after visits to unknown sites.
How to Mitigate CVE-2026-17858
Immediate Actions Required
- Update Google Chrome on all Windows endpoints to version 151.0.7922.72 or later.
- Restart the browser after applying the update to ensure the patched binaries are loaded.
- Verify enterprise Chrome deployment tools are configured to deliver stable channel updates without user intervention.
Patch Information
Google released the fix in Chrome Stable channel 151.0.7922.72 for Windows. Review the Chrome Releases stable channel update and the corresponding Chromium tracker issue for full disclosure details. Downstream Chromium-based browsers should ship equivalent fixes; consult individual vendor advisories.
Workarounds
- Enforce automatic updates through the Chrome Enterprise policy UpdateDefault to guarantee timely patch delivery.
- Restrict WebNN exposure by disabling experimental web platform features via the EnableExperimentalPolicies and related enterprise policies where feasible.
- Apply web filtering to block access to untrusted or newly registered domains until endpoints are patched.
# Verify installed Chrome version on Windows via PowerShell
(Get-Item "C:\Program Files\Google\Chrome\Application\chrome.exe").VersionInfo.ProductVersion
# Force Chrome update check through Google Update
& "C:\Program Files (x86)\Google\Update\GoogleUpdate.exe" /ua /installsource scheduler
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
