CriticalCVE-2025-6554

    Google Chromium V8 Type Confusion Vulnerability (CVE-2025-6554)

    Published In CISA KEV since Sources: BSI, SingCERT, Debian, pwn.watch, CVE.org, Msrc Update Guide

    What is affected, what to do

    Type confusion in V8 in Google Chrome prior to 138.0.7204.96 allowed a remote attacker to perform arbitrary read/write via a crafted HTML page. (Chromium security severity: High)

    The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Conflicting version data — version display is hidden until the data is resolved.

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    8.1

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    8.1

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: BSI, SingCERT, Debian, pwn.watch, CVE.org, Msrc Update Guide

    14.1 %

    EPSS score

    Elevated — model estimates 10-50% exploitation likelihood.

    Source: FIRST EPSS, percentile 96.6

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    224.73 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: VulnCheck KEV (opens in a new tab), CSA/SingCERT How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    8.1 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    8.1
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

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    14.1 %
    Elevated — model estimates 10-50% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    96.6
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 17 July 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-843

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable without authentication and needs only a single user action (visiting a crafted page). It yields arbitrary read/write inside the renderer, making it the classic first stage of a drive-by or watering-hole chain paired with a sandbox escape. Chromium zero-days of this kind are typically used in targeted operations against high-value individuals such as administrators, executives, journalists, and government or critical-infrastructure staff. Exploitation likelihood is very high, though CISA records no known ransomware use. Because browsers sit on virtually every endpoint and a patch exists, treat this as "critical — patch and force relaunch within 24-72 h". Server-side headless renderers rank lower but still matter if they ever process external content.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Push Chrome to 138.0.7204.96 (or 138.0.7204.92 depending on platform build) or later across the estate. Then force a relaunch, because the fix only takes effect after restart. Set RelaunchNotification = 2 (required) and a short RelaunchNotificationPeriod via GPO/Intune.
      • Update Microsoft Edge to 138.0.3351.65 or later. Opera, Brave, Vivaldi and other Chromium-based browsers are also affected. Patch available from the vendor — look up the fixed version in the vendor advisory.
      • Update Chrome for Android via Managed Google Play/MDM. The context lists Android builds below 138.0.7204.63 as affected. Confirm the exact fixed build in the Chrome release notes.
      • Don't forget server-side headless Chromium: upgrade Grafana Image Renderer to 3.12.9 and Grafana Synthetic Monitoring Agent to 0.38.3. Rebuild container images and redeploy pods.
      • Reconcile inventory against reality. Query EDR/vulnerability management for hosts running Chrome below 138.0.7204.92 or Edge below 138.0.3351.65. Chase systems without a working updater: kiosks, VDI golden images and jump hosts.
      • Prioritise high-value users: patch admin workstations/PAWs, executives and finance staff first. Block browsing from unpatched systems in that group until updated.

    2. Runbook step 2

      Mitigation layers

      • Browser configuration (shrink the V8 JIT attack surface): where patching is delayed, set the Chrome policy DefaultJavaScriptJitSetting = 2 to block JIT. Allow-list trusted business apps via JavaScriptJitAllowedForSites. In Edge, enforce Enhanced Security Mode in strict mode (EnhanceSecurityMode = 2). This reduces risk but does not replace patching.
      • Network/web gateway: block or isolate (remote browser isolation) newly registered and uncategorised domains at the proxy/SWG. This matters most for links arriving via email and messaging, since exploitation requires a crafted HTML page.
      • Endpoint hardening: use WDAC/AppLocker to prevent executables launching from %LOCALAPPDATA%, %TEMP% and download paths. Enable Defender ASR rules, notably "Block executable files from running unless they meet a prevalence, age, or trusted list criterion".
      • IAM/least privilege: remove local admin rights from standard users. Technically prevent web browsing with privileged accounts, for example through proxy rules keyed on admin group membership. This limits the blast radius of a sandbox-escape plus privilege-escalation chain.
      • Segment server-side renderers: restrict Grafana Image Renderer and Synthetic Monitoring agents to approved internal Grafana URLs only. Deny general internet egress via Kubernetes NetworkPolicy or firewall so they never render attacker-controlled HTML.
      • Protect the update channel: verify that UpdateDefault/AutoUpdateCheckPeriodMinutes are not disabled by policy. Air-gapped segments need an internal update mirror.

    3. Runbook step 3

      Detection rules

      • Anomalous renderer child processes (Sysmon EID 1 / Security 4688): chrome.exe or msedge.exe spawning cmd.exe, powershell.exe, rundll32.exe, mshta.exe or wscript.exe. KQL: DeviceProcessEvents | where InitiatingProcessFileName in~ ("chrome.exe","msedge.exe") and FileName in~ ("cmd.exe","powershell.exe","rundll32.exe","mshta.exe","wscript.exe")
      • Browser writing payloads outside the Downloads folder (Sysmon EID 11): the browser drops .exe, .dll or .ps1 into %TEMP%, %APPDATA% or autostart locations, followed by execution within minutes. Implement as a Sigma correlation: file_event + process_creation, same host, 5-minute window.
      • Linux/containers (auditd execve): ppid resolves to chrome, chromium or chrome-headless-shell, and exe is /bin/sh, /bin/bash, curl or wget. This is high-fidelity in Grafana renderer pods, where any shell spawn is anomalous.
      • Renderer crashes as early warning: clusters of Crashpad dumps or WER events (Application Event ID 1000/1001 for chrome.exe/msedge.exe) shortly after a visit to a previously unseen domain. Failed exploit attempts frequently crash the renderer.
      • Version compliance as a detection: run a daily report DeviceTvmSoftwareInventory | where SoftwareName has "chrome" and SoftwareVersion < "138.0.7204.92", with an equivalent for Edge. Flag separately the processes still running old images because a relaunch is pending.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Type confusion in V8 in Google Chrome prior to 138.0.7204.96 allowed a remote attacker to perform arbitrary read/write via a crafted HTML page. (Chromium security severity: High)

    Source: BSI CSAF, BSI WID Portal, CSA/SingCERT, Debian Security Advisories, pwn.watch, NVD (NIST), Microsoft Security Update Guide, cvelistv5, CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    GoogleChrome
    • < 138.0.7204.96
    • <138.0.7204.63 Android
    • < 138.0.7204.96
    • 138.0.7204.96
    • —
    • 138.0.7204.96
    googlechrome
    • < 138.0.7204.92
    • < 138.0.7204.96
    • 138.0.7204.92
    • 138.0.7204.96
    GrafanaGrafana Image Renderer
    • < 3.12.9
    • 3.12.9
    GrafanaGrafana Synthetic Monitoring Agent
    • < 0.38.3
    • 0.38.3
    MicrosoftEdge
    • < 138.0.3351.65
    • 138.0.3351.65

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianchromiumbookworm

    Weakness classes (CWE)

    • CWE-843Access of Resource Using Incompatible Type ('Type Confusion')

      Base

      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.

      Entry at MITRE CWE-843

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    CSA/SingCERTActive Exploitation of Zero-Day Vulnerability in Google Chrome (opens in a new tab)CSA/SingCERTactively exploited

    References & sources

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