CVE-2026-78999: Google Chrome Privilege Escalation Flaw

CVE-2026-78999 Overview

CVE-2026-78999 is an improper privilege management flaw [CWE-269] in the Navigation component of Google Chrome versions prior to 152.0.7977.65. A remote attacker who has already compromised the renderer process can leverage social engineering to escape the Chrome sandbox and execute arbitrary code on the host. Exploitation requires user interaction and a crafted HTML page. Google assigned the issue a Chromium security severity of Medium, while the NVD-scored vector produces a higher rating due to the scope change and impact on confidentiality, integrity, and availability.

Critical Impact
Successful exploitation allows arbitrary code execution outside the browser sandbox, giving attackers a foothold on the underlying operating system.

Affected Products

Google Chrome for Desktop versions prior to 152.0.7977.65
Chromium-based builds incorporating the vulnerable Navigation logic
Downstream browsers that had not yet merged the upstream Chromium fix at publication time

Discovery Timeline

2026-08-25 - CVE-2026-78999 published to the National Vulnerability Database
2026-08-27 - Last updated in NVD database

Technical Details for CVE-2026-78999

Vulnerability Analysis

The vulnerability resides in Chrome's Navigation handling, where privilege boundaries between the sandboxed renderer and higher-privileged browser components are not correctly enforced. An attacker who already controls a compromised renderer process can chain this flaw with a user-interaction step, such as clicking a crafted link or confirming a navigation prompt, to break out of the sandbox. Once outside the sandbox, code runs with the privileges of the browser process, giving the attacker direct access to local resources.

The issue is categorized under [CWE-269: Improper Privilege Management]. The Chromium project tracks the underlying defect in Chromium Issue Tracker #497957278.

Root Cause

Navigation transitions in Chrome must revalidate privileges when moving between security principals. The vulnerable code path failed to enforce this boundary correctly, permitting the renderer to influence navigation state in a way that yielded elevated privileges. Because the sandbox depends on strict privilege separation, a mistake in Navigation logic translates directly into a sandbox escape primitive.

Attack Vector

Exploitation is network-reachable but non-trivial. The attacker must first achieve renderer compromise, typically through a separate memory-corruption bug, and then coax the victim into an interaction such as clicking a link or accepting a prompt on an attacker-controlled HTML page. The combination of a compromised renderer, user interaction, and the Navigation flaw produces a scope-changing outcome: code executes outside the browser's sandboxed process boundary.

No public proof-of-concept, exploit database entry, or CISA KEV listing exists for CVE-2026-78999 at the time of publication.

Detection Methods for CVE-2026-78999

Indicators of Compromise

Chrome browser processes spawning unexpected child processes such as cmd.exe, powershell.exe, or shell interpreters on Windows, macOS, or Linux hosts
Unexpected file writes or persistence artifacts under user profile directories following a browsing session
Outbound connections from Chrome-spawned processes to previously unseen infrastructure hosting HTML payloads

Detection Strategies

Inventory Chrome installations across managed endpoints and flag any build below 152.0.7977.65
Monitor parent-child process relationships where chrome.exe or platform equivalents spawn native binaries outside expected helper processes
Correlate renderer crashes with subsequent process launches, since renderer compromise commonly precedes sandbox-escape attempts

Monitoring Recommendations

Ingest browser process telemetry and Chrome update events into a centralized data lake for longitudinal analysis
Alert on execution of scripting interpreters or LOLBins with a Chrome ancestor in the process tree
Track user-interaction phishing lures that direct victims to crafted HTML pages, particularly those requesting a click-through or navigation confirmation

How to Mitigate CVE-2026-78999

Immediate Actions Required

Update Google Chrome to version 152.0.7977.65 or later on all managed endpoints
Force browser restart after deployment so the patched binary is loaded into memory
Verify Chromium-based derivative browsers have merged the upstream fix before treating them as remediated

Patch Information

Google addressed CVE-2026-78999 in the Chrome Stable channel update documented in the Google Chrome Stable Update. The fix is included in Chrome 152.0.7977.65 for Desktop. Enterprise administrators should confirm rollout through their standard update management channel and validate installed versions against the fixed build.

Workarounds

Enforce Chrome auto-update policies through group policy or MDM so security releases apply without user action
Restrict execution of untrusted HTML content and block known phishing domains at the network perimeter
Apply application control policies that prevent Chrome from launching scripting interpreters or unsigned binaries

bash

# Verify installed Chrome version on Linux endpoints
google-chrome --version

# Windows PowerShell: query installed Chrome version from the registry
Get-ItemProperty "HKLM:\SOFTWARE\Google\Update\Clients\*" |
  Where-Object { $_.name -eq "Google Chrome" } |
  Select-Object name, pv