CVE-2025-6554
Google Chromium V8 — Google Chromium V8 Type Confusion Vulnerability
Description
Response & Mitigation
Why act now?
Prioritisation rationale
CVE-2025-6554 is a type confusion flaw in the V8 JavaScript engine that requires no authentication and only minimal user interaction — visiting a crafted web page — to achieve arbitrary read/write within the browser process, making it a reliable first stage in renderer-to-sandbox-escape exploit chains. The CVSS v3 score of 8.1 (AV:N/AC:L/PR:N/UI:R) combined with an EPSS score in the 96th percentile indicates a very high probability of broad exploitation. Organisations most exposed are those with large knowledge-worker populations, Grafana monitoring stacks running the Image Renderer plugin, and environments where browser updates are not centrally enforced. The CISA known-ransomware flag is not set, so the immediate priority is rapid patch deployment and post-exploitation detection rather than broad network isolation.
Runbook · Step 1
Immediate response (0-24 h)
- Google Chrome: Update to version 138.0.7204.96 or later (Stable Channel Update, released approximately 2025-07-01). On Android, all versions below 138.0.7204.63 are vulnerable — force update via Google Play or MDM policy.
- Microsoft Edge: Update to version 138.0.3351.65 or later. Deploy via Microsoft Update Catalog, WSUS, or Intune; verify with
msedge --versionor Group Policy reporting. - Grafana Image Renderer: Update to version 3.12.9 or later. Grafana Synthetic Monitoring Agent: Update to version 0.38.3 or later. Both embed Chromium and must be patched independently — Grafana core instances without these plugins are not directly affected.
- Inventory all other Chromium-based browsers in the environment (Opera, Brave, Vivaldi, etc.) and check vendor advisories for patch availability — verify version numbers in the respective vendor advisory.
- Until patch rollout is complete: restrict browser access to untrusted external sites via proxy filtering and block JavaScript execution on unknown domains using Content Security Policy or browser policy.
Runbook · Step 2
Mitigation layers
- Network segmentation: Move workstations that cannot be patched immediately into a restricted VLAN; allow outbound HTTP/HTTPS (TCP 80/443) only through a TLS-inspecting proxy.
- WAF/IPS rule: Configure Suricata/Snort to flag HTTP responses with abnormally large or deeply nested JavaScript payloads; apply
Content-Lengththresholds on responses withContent-Type: text/htmlorapplication/javascript. Refine signatures against PoC samples once publicly available. - Endpoint hardening: Enforce the
SitePerProcessChrome/Edge policy (Strict Site Isolation) to reduce renderer exploit impact. On Windows:HKLM\SOFTWARE\Policies\Google\Chrome\SitePerProcess = 1. - IAM / least privilege: Ensure browser processes run without administrative rights; confirm end-user accounts hold no local admin role (principle of least privilege per your organisation's tiering model).
- Grafana-specific: Disable Image Renderer and Synthetic Monitoring Agent until patched if they are not operationally critical. Place Grafana behind an authentication proxy and block direct internet access to Grafana ports (default: TCP 3000).
Runbook · Step 3
Detection rules
- Browser telemetry / EDR — process ancestry: Alert on
chrome.exeormsedge.exespawning unexpected child processes. Sigma shape:ParentImage|endswith: 'chrome.exe' AND Image|endswith: ('cmd.exe','powershell.exe','wscript.exe'). - Sysmon EID 1 / EID 10 — process access: Renderer processes accessing memory of processes outside the browser sandbox (e.g.,
lsass.exe,explorer.exe). KQL:DeviceProcessEvents | where InitiatingProcessFileName =~ "chrome.exe" and FileName in ("lsass.exe","explorer.exe"). - Windows Event ID 4688 / auditd execve: Execution of binaries dropped into the browser profile directory (
%LOCALAPPDATA%\Google\Chrome\) or user temp directories — strong indicator of sandbox escape and payload staging. - Network telemetry (Zeek/Suricata): Outbound connections from
chrome.exeormsedge.exeto unknown IPs on non-standard ports (not 80/443) immediately after visiting an external site — potential C2 beacon following successful exploitation. - Grafana logs: HTTP requests to the Image Renderer endpoint (
/render) with unusually long or encoded URL parameters; renderer error logs containing V8 exceptions or segmentation faults as indicators of exploit attempts.
Metrics
Weakness classes (CWE)
CWE-843Base
Access of Resource Using Incompatible Type ('Type Confusion')
The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.
cwe.mitre.org →
Affected products
Products and version ranges extracted from the vendor/CERT advisory. A range like „<4.14.6“ implies the update recommendation „upgrade to 4.14.6 or later“.
Google
Chrome<138.0.7204.63 Android
Google
Chrome< 138.0.7204.96
fixed in 138.0.7204.96
Grafana
GrafanaImage Renderer <3.12.9
Grafana
GrafanaSynthetic Monitoring Agent <0.38.3
Microsoft
Edge< 138.0.3351.65
fixed in 138.0.3351.65
Public exploit references
Public proof-of-concepts and detection templates for this vulnerability. Maturity ranges from reported PoCs through working detection scripts up to fully weaponized exploit modules. NEOSEC mirrors the code internally for forensic analysis; externally we only link to the original sources.