CriticalCVE-2026-3909

    Google Skia Out-of-Bounds Write Vulnerability (CVE-2026-3909)

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

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    What is affected, what to do

    Out of bounds write in Skia in Google Chrome prior to 146.0.7680.75 allowed a remote attacker to perform out of bounds memory access 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

    8.8

    Priority

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

    Source: NVD, CVSS v3

    8.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: pwn.watch, Debian, CVE.org, Msrc Update Guide, SUSE, Red Hat, BSI

    2.3 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 83.6

    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
    214.93 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) 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
    8.8 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
    8.8
    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“.

    Read in glossary
    2.3 %
    Moderate — model estimates 1-10% 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
    83.6
    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 13 March 2026
    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-787

    Response and mitigation

    Why act now?

    Prioritisation rationale

    The flaw is network-reachable without authentication and needs only a user to open a crafted page, which makes it a natural fit for watering-hole and malvertising campaigns. These are typically chained with a sandbox escape to achieve full host compromise. Exploitation likelihood is elevated but not top-tier, and CISA does not flag known ransomware use, yet the KEV listing confirms real-world exploitation. The sheer footprint of Chrome, Chromium derivatives, Android and WebKitGTK means virtually every organisation is exposed. Treat this as high priority: aim to patch all clients within 24-72 h, and act immediately for high-exposure user groups and any host with access to KRITIS-relevant networks.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Update Google Chrome fleet-wide to 146.0.7680.75 or later. The vendor data also lists 146.0.7680.80 as a fixed build. Then force a browser relaunch, because a downloaded-but-not-restarted update does not protect anything. Enforce the relaunch via the RelaunchNotification=2 policy with a short RelaunchNotificationPeriod.
      • Inventory every Chromium-based browser and runtime (Microsoft Edge, Brave, Opera, Vivaldi, Electron apps). Patches are available from each vendor; look up the exact fixed version in the vendor advisory and ship the updates in the same change window.
      • Upgrade WebKitGTK on Linux to 2.54.0. On Debian 13 the package is webkit2gtk 2.54.0-1~deb13u1 (apt update && apt install --only-upgrade libwebkit2gtk-4.1-0 libjavascriptcoregtk-4.1-0; verify package names for your ABI). Mail clients and desktop apps that embed WebKitGTK, such as Evolution or GNOME Web, are in scope too.
      • Push updates to ChromeOS devices, managed Android devices (Chrome/WebView) and in-house Flutter apps via MDM or your build pipeline. Patches are available from the vendor; look up the version in the relevant advisory. Flutter apps need a rebuild against the fixed engine.
      • Once the deadline passes, use NAC or Conditional Access to block unpatched clients from crown-jewel applications. At a minimum, cut them off from uncategorised web destinations.

    2. Runbook step 2

      Mitigation layers

      • Configuration / patch enforcement: Set UpdateDefault=1 via Chrome ADMX or Intune and remove any TargetVersionPrefix pinning to old versions. Verify that no GPO disables the Google Update service.
      • Network / web gateway: Block or isolate the "newly registered domains", "uncategorised" and "ad networks/malvertising" categories at the proxy or SWG. Exploitation only requires rendering a crafted HTML page, so shrinking the drive-by surface is the strongest compensating control.
      • Remote browser isolation: For high-risk groups (executives, finance, OT engineering workstations), route non-allowlisted browsing through RBI so that untrusted content never renders on the endpoint.
      • Endpoint hardening: Never run browsers with admin rights, remove local admin rights, and audit shortcuts for --no-sandbox. Enable Windows Exploit Protection (CFG, ACG) or EDR exploit prevention for chrome.exe/msedge.exe.
      • Optional surface reduction: Setting DefaultJavaScriptJitSetting=2 disables the V8 JIT on untrusted sites. It does not fix the Skia bug, but it raises the cost of typical exploit chains that use JavaScript for heap grooming.
      • OT / KRITIS networks: Keep engineering and HMI hosts off general web browsing. Where a browser is unavoidable, allow only allowlisted destinations via a jump host.

    3. Runbook step 3

      Detection rules

      • Suspicious process ancestry (Sysmon EID 1 / EDR): A browser process spawning shells or LOLBins suggests a successful renderer exploit plus sandbox escape. KQL: DeviceProcessEvents | where InitiatingProcessFileName in~ ("chrome.exe","msedge.exe") and FileName in~ ("cmd.exe","powershell.exe","pwsh.exe","mshta.exe","rundll32.exe","regsvr32.exe","wscript.exe")
      • Renderer crash clusters (Windows Event ID 1000/1001, Application Error): Look for faulting application chrome.exe or module chrome.dll/msedge.dll with access violation 0xc0000005. Repeated crashes after visiting the same URL point to exploit attempts. Correlate with proxy logs for the same time window.
      • Linux (auditd/journald): Look for SIGSEGV entries for WebKitWebProcess or Chrome renderers (journalctl | grep -E "WebKitWebProcess|chrome.*segfault"). Add auditd execve rules that fire when the parent is WebKitWebProcess or chrome and the child is /bin/sh, bash, curl or wget.
      • Exposure inventory as detection: KQL: DeviceTvmSoftwareInventory | where SoftwareName has "chrome" | where parse_version(SoftwareVersion) < parse_version("146.0.7680.75"). Send the results to the patch team as a daily report.
      • Network (Zeek/Suricata/proxy): Watch for first-seen domain visits followed immediately by new outbound connections from the host to rare destinations, or by executable downloads. Build this on http.log/files.log with MIME type application/x-dosexec and the referrer chain.

    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

    Out of bounds write in Skia in Google Chrome prior to 146.0.7680.75 allowed a remote attacker to perform out of bounds memory access via a crafted HTML page. (Chromium security severity: High)

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

    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
    • < 146.0.7680.75
    • 146.0.7680.75
    googlechrome
    • < 146.0.7680.80
    • 146.0.7680.80
    Open SourceWebKitGTK
    • < 2.54.0
    • 2.54.0

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianchromiumbookworm
    Linuxdebianchromiumtrixie
    Linuxdebianwebkit2gtktrixie

    Weakness classes (CWE)

    • CWE-787Out-of-bounds Write

      Base

      The product writes data past the end, or before the beginning, of the intended buffer.

      Entry at MITRE CWE-787

    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

    References & sources

    • issues.chromium.orgissues/491421267Permissions required
    • chromereleases.googleblog.com2026/03/stable-channel-update-for-desktop_13.htmlRelease notes, Vendor advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-3909government-resource, US government resource
    • pwn.watchpwn.watch: Chrome zero-days CVE-2026-3909 (Skia) and CVE-2026-3910 (V8)pwn-watch
    • bleepingcomputer.comBleepingComputer Chrome zero-day rounduppwn-watch
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    Badge preview for CVE-2026-3909
    <a href="https://intel.neosec.eu/en/cve/CVE-2026-3909"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-3909.svg?lang=en" alt="CVE-2026-3909 – NEOSEC Intel" height="20"></a>