CVE-2026-13940: Google Chrome Information Disclosure Flaw

CVE-2026-13940 Overview

CVE-2026-13940 is an uninitialized memory use vulnerability [CWE-457] in the Cast component of Google Chrome versions prior to 150.0.7871.47. An attacker positioned on the same local network segment can send malicious network traffic to a vulnerable Chrome instance. This traffic triggers the Cast component to read uninitialized memory, potentially exposing sensitive contents of the browser process. Google classified the Chromium security severity as Medium and addressed the flaw in the stable channel update for desktop.

Critical Impact
An adjacent-network attacker can leak potentially sensitive information from Chrome process memory by sending crafted Cast protocol traffic, with no user interaction or authentication required.

Affected Products

Google Chrome for Desktop versions prior to 150.0.7871.47
Chromium-based builds incorporating the vulnerable Cast component
All supported desktop platforms (Windows, macOS, Linux) running affected Chrome versions

Discovery Timeline

2026-06-30 - CVE-2026-13940 published to NVD
2026-07-02 - Last updated in NVD database

Technical Details for CVE-2026-13940

Vulnerability Analysis

The vulnerability resides in the Cast subsystem of Google Chrome, which handles media casting to devices such as Chromecast receivers over the local network. Chrome uses uninitialized memory when processing certain Cast protocol messages, and portions of that memory are returned in responses or otherwise observable by the network peer. Because the attacker must reside on the same local network segment (adjacent network), remote internet-based exploitation is not feasible. However, the flaw requires no authentication, no user interaction, and no privileges to exploit, and the leaked memory may contain browser secrets such as tokens, URLs, or fragments of user data.

Root Cause

The root cause is a failure to initialize a memory region before use, categorized under [CWE-457] Use of Uninitialized Variable. When the Cast component processes attacker-supplied network input, it constructs response or handling structures using fields that were never assigned deterministic values. The residual contents of heap or stack memory are then consumed as if they were valid data, and this residue can be inferred by an attacker who observes or receives the resulting traffic. Additional technical detail is tracked in the Chromium Issue Tracker Entry.

Attack Vector

Exploitation requires network adjacency, such as sharing a Wi-Fi network, a corporate LAN, or a compromised broadcast domain with the victim. The attacker sends malicious Cast discovery or session traffic to the Chrome instance. Chrome parses this traffic through the vulnerable code path and emits or processes data derived from uninitialized memory. The attacker then extracts the leaked bytes to reconstruct sensitive process memory contents over repeated interactions.

No verified public exploit code is available for CVE-2026-13940. Refer to the Google Chrome Stable Update advisory for vendor-authoritative technical context.

Detection Methods for CVE-2026-13940

Indicators of Compromise

Unexpected Cast discovery or session traffic on TCP/UDP port 8009 and mDNS _googlecast._tcp from unrecognized hosts on the local segment.
Chrome renderer or utility processes generating unusual outbound traffic to non-Chromecast local peers.
Repeated malformed Cast protocol handshakes originating from a single host on the LAN.

Detection Strategies

Inventory installed Chrome versions across managed endpoints and flag any build below 150.0.7871.47.
Deploy network monitoring rules that baseline legitimate Cast/mDNS traffic and alert on anomalous senders or message volumes.
Correlate endpoint telemetry with network logs to identify Chrome processes interacting with unknown Cast peers.

Monitoring Recommendations

Enable browser version telemetry through enterprise management (Chrome Browser Cloud Management) to continuously track patch state.
Monitor DNS-SD and mDNS traffic on corporate wireless networks for rogue Cast advertisements.
Log and review network segments that permit multicast traffic between untrusted client VLANs.

How to Mitigate CVE-2026-13940

Immediate Actions Required

Update Google Chrome to version 150.0.7871.47 or later on all Windows, macOS, and Linux endpoints.
Restart Chrome after applying the update to ensure the patched binary is loaded.
Verify enterprise Chrome update policies are not deferring the stable channel beyond acceptable risk windows.

Patch Information

Google released the fix in the stable channel update documented at the Google Chrome Stable Update. Administrators should validate that managed installations report a version at or above 150.0.7871.47. Chromium-derived browsers should pull the corresponding upstream fix from the merge referenced in the Chromium Issue Tracker Entry.

Workarounds

Disable the Chrome media router or Cast functionality via enterprise policy (EnableMediaRouter=false) where casting is not required.
Segment guest and untrusted Wi-Fi networks from corporate endpoints to remove adjacent-network reachability.
Block mDNS and Cast protocol traffic (_googlecast._tcp, port 8009) between untrusted VLANs at the network layer until patching completes.

bash

# Configuration example: disable Chrome media router via enterprise policy
# Windows registry (HKLM)
reg add "HKLM\Software\Policies\Google\Chrome" /v EnableMediaRouter /t REG_DWORD /d 0 /f

# macOS (plist)
defaults write com.google.Chrome EnableMediaRouter -bool false

# Linux (managed policy JSON at /etc/opt/chrome/policies/managed/cast.json)
{
  "EnableMediaRouter": false
}