CriticalCVE-2023-4863

    Google Chromium WebP Heap-Based Buffer Overflow Vulnerability (CVE-2023-4863)

    Published In CISA KEV since Sources: SingCERT, Debian, OSV, pwn.watch, CVE.org

    What is affected, what to do

    Heap buffer overflow in libwebp in Google Chrome prior to 116.0.5845.187 and libwebp 1.3.2 allowed a remote attacker to perform an out of bounds memory write via a crafted HTML page. (Chromium security severity: Critical)

    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: SingCERT, Debian, OSV, pwn.watch, CVE.org

    99.98 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.98

    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
    227.40 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: 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
    8.8 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
    99.98 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    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
    99.98
    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

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable without authentication and needs only minimal user interaction, such as rendering a page or message. It sits among the CVEs most likely to be exploited anywhere and has been used in zero-click and drive-by chains against mobile and desktop users. CISA does not flag ransomware use. The real risk is breadth: libwebp is embedded in browsers, Electron apps, imaging libraries and server pipelines, so patching Chrome alone does not close the exposure. Treat it as critical. Patch internet-facing clients, privileged users and server-side upload processing first, then run a systematic hunt for embedded copies.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Push Google Chrome 116.0.5845.187 or later fleet-wide and force a browser restart via policy (RelaunchNotification = 2 with a short RelaunchNotificationPeriod). A staged but unrestarted update leaves the endpoint vulnerable.
      • Update every other Chromium-based browser (Microsoft Edge, Brave, Opera, Vivaldi) and Mozilla Firefox to the vendor's current release. The context does not list versions for these: a patch is available from the vendor, so check the vendor advisory for the exact build.
      • On Linux, upgrade libwebp to 1.3.2 or the distro-backported fix. Per the context, Debian 10, 11 and 12 and Fedora 39 are affected (apt list --installed | grep libwebp, rpm -q libwebp). Then restart any long-running service that has the library loaded (lsof | grep libwebp).
      • Hunt your software inventory for bundled libwebp copies: Electron apps (chat, collaboration and password-manager clients), image viewers and line-of-business tools. The context names bandisoft Honeyview (fixed in 5.51) and Bentley Seequent Leapfrog (fixed in 2023.2). Search for libwebp*.so*, libwebp*.dll and statically linked Electron binaries.
      • Fast-track server-side image pipelines (upload thumbnailers, CMS, document converters, container images shipping ImageMagick, Pillow or libvips). These decode untrusted WebP with zero user interaction.

    2. Runbook step 2

      Mitigation layers

      • Configuration/endpoint: On Firefox clients that cannot update immediately, disable WebP decoding via enterprise policy (image.webp.enabled = false). Chrome has no equivalent kill switch, so patching is the only effective control there.
      • Network/proxy: On the secure web gateway, block Content-Type: image/webp responses from uncategorised, newly registered or low-reputation domains, or route them through remote browser isolation until patch compliance is confirmed.
      • Mail and messaging gateway: Quarantine or CDR-flatten WebP attachments and inline WebP in external HTML mail.
      • Endpoint hardening: Make sure no policy or shortcut disables the Chrome sandbox or Site Isolation (hunt for --no-sandbox). Enable EDR or Defender ASR rules that block browser and Electron processes from spawning shells or script hosts.
      • Server segmentation: Run image-processing workers isolated, with egress denied and seccomp/AppArmor profiles applied, so a successful heap corruption stays contained to the container.
      • IAM: Keep privileged accounts off general web browsing on unpatched hosts. Use privileged access workstations without open internet access for admin work.

    3. Runbook step 3

      Detection rules

      • Crash telemetry: Look for clusters of Windows Application log Event ID 1000/1001 with faulting app chrome.exe, msedge.exe, firefox.exe or an Electron binary and exception 0xc0000005 shortly after a specific URL visit. On Linux, the equivalent is SIGSEGV in coredumpctl/journald with libwebp in the stack.
      • Process ancestry (Sysmon EID 1 / EDR): Sigma shape: ParentImage|endswith: ['\chrome.exe','\msedge.exe','\firefox.exe'] AND Image|endswith: ['\cmd.exe','\powershell.exe','\rundll32.exe','\mshta.exe','\wscript.exe']. KQL: DeviceProcessEvents | where InitiatingProcessFileName in~ ("chrome.exe","msedge.exe") and FileName in~ ("cmd.exe","powershell.exe","rundll32.exe").
      • File and persistence artefacts: Watch Sysmon EID 11 and 13 for executables or Run-key writes by a browser process outside the downloads folder. On Linux, use auditd execve events whose ppid resolves to a browser or thumbnailer process.
      • Network (Zeek/Suricata): Filter files.log for mime_type == "image/webp" from rare domains and correlate with subsequent browser crashes. Enable Suricata/ET signatures for malformed VP8L Huffman tables in WebP if your ruleset ships them.
      • Server side: Check web logs for .webp uploads followed by HTTP 500 errors or worker restarts. Treat unexpected outbound connections from image-processing containers as a high-fidelity alert.

    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

    Heap buffer overflow in libwebp in Google Chrome prior to 116.0.5845.187 and libwebp 1.3.2 allowed a remote attacker to perform an out of bounds memory write via a crafted HTML page. (Chromium security severity: Critical)

    Source: CSA/SingCERT, Debian Security Advisories, OSV (Open Source Vulnerabilities), pwn.watch, NVD (NIST), 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
    • < 116.0.5845.187
    • 116.0.5845.187
    Googlelibwebp
    • < 1.3.2
    • 1.3.2
    bandisofthoneyview
    • < 5.51
    • 5.51
    bentleyseequent_leapfrog
    • < 2023.2
    • 2023.2
    googlechrome
    • < 116.0.5845.187
    • 116.0.5845.187
    microsoftedge_chromium
    • < 116.0.1938.81
    • 116.0.1938.81
    microsoftteams
    • < 1.6.00.26474
    • < 1.6.00.26463
    • 1.6.00.26474
    • 1.6.00.26463
    microsoftwebp_image_extension
    • < 1.0.62681.0
    • 1.0.62681.0
    mozillafirefox
    • < 117.0.1
    • < 102.15.1
    • 115.1.0 – < 115.2.1
    • 117.0.1
    • 102.15.1
    • 115.2.1
    mozillathunderbird
    • < 102.15.1
    • 115.0 – < 115.2.2
    • 102.15.1
    • 115.2.2
    netappactive_iq_unified_manager
    • —
    • —
    webmprojectlibwebp
    • < 1.3.2
    • 1.3.2
    androidplatform/external/webp
    • 12L
    • 13:0
    • 14-next
    • 13
    • 11:0
    • 14-next:0
    • 12L:0
    • 12:0
    • 12
    • 11
    • —
    • 13:2023-10-06
    • —
    • —
    • 11:2023-10-06
    • 14-next:2023-10-06
    • 12L:2023-10-06
    • 12:2023-10-06
    • —
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebiandebian_linux10.0
    Linuxdebiandebian_linux11.0
    Linuxdebiandebian_linux12.0
    Linuxdebianfirefox-esrbookworm
    Linuxdebianfirefox-esrbullseye
    Linuxdebianlibwebpbookworm
    Linuxdebianlibwebpbullseye
    Linuxdebianthunderbirdbookworm
    Linuxdebianthunderbirdbullseye
    Otherfedoraprojectfedora37
    Otherfedoraprojectfedora38
    Otherfedoraprojectfedora39

    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 High-Severity Vulnerability in Android Devices (opens in a new tab)CSA/SingCERTactively exploited
    CSA/SingCERTActive Exploitation of Zero-day Vulnerability in Google Chrome (opens in a new tab)CSA/SingCERTactively exploited
    CSA/SingCERTCritical Zero-day Vulnerability in Mozilla Firefox & Thunderbird (opens in a new tab)CSA/SingCERTactively exploited

    References & sources

    Linked advisories

    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2023-4863
    <a href="https://intel.neosec.eu/en/cve/CVE-2023-4863"><img src="https://intel.neosec.eu/badge/cve/CVE-2023-4863.svg?lang=en" alt="CVE-2023-4863 – NEOSEC Intel" height="20"></a>