CriticalCVE-2024-40766

    SonicWall SonicOS Improper Access Control Vulnerability (CVE-2024-40766)

    Published Last modified In CISA KEV since Sources: CVE.org, NCSC NZ, pwn.watch

    What is affected, what to do

    An improper access control vulnerability in SonicWall SonicOS allows unauthorized resource access and can cause the firewall to crash under certain conditions. This affects SonicWall Firewall Gen 5, Gen 6, and Gen 7 devices running SonicOS 7.0.1-5035 and older versions. The vulnerability is actively exploited in ransomware campaigns. Immediate patching to the latest version is critical to mitigate this risk.

    The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. 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.

    Affected
    • SonicWall SonicOS eq 5.9.2.14-12o and older versions..5.9.2.14-12o and older versions
    • SonicWall SonicOS eq 6.5.4.14-109n and older versions..6.5.4.14-109n and older versions
    • SonicWall SonicOS eq 7.0.1-5035 and older versions..7.0.1-5035 and older versions

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

    Metrics

    9.8

    Priority

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

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: CVE.org, NCSC NZ, pwn.watch

    18.4 %

    EPSS score

    Elevated — model estimates 10-50% exploitation likelihood.

    Source: FIRST EPSS, percentile 97.2

    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
    255.72 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: ANSSI / CERT-FR, NCSC NZ 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
    9.8 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
    9.8
    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
    18.4 %
    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
    97.2
    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
    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-284

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is network-reachable without authentication or user interaction, and it sits on a perimeter device that gates access to the entire internal network. CISA flags it for known ransomware campaign use; the typical pattern is initial access via SSLVPN with local accounts lacking MFA, followed by rapid lateral movement and encryption within hours. Exploitation likelihood is very high, and targets skew towards mid-market organisations running internet-exposed SonicWall appliances. Treat any internet-reachable SonicWall management interface or SSLVPN as a critical emergency; without internet exposure, urgency remains high but the fix can follow a scheduled change.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Record every SonicWall firewall (Gen 5, Gen 6, Gen 7) together with its firmware build. Affected are Gen 5 and Gen 6, plus Gen 7 on SonicOS 7.0.1-5035 or older. The builds listed in the context (5.9.2.14-13o, 6.5.2.8-2n, 6.5.4.15.116n, 7.0.1-5035) mark the version boundaries. Confirm the exact fixed build per model in the SonicWall PSIRT advisory for CVE-2024-40766.
      • Upgrade firmware: Apply the vendor-fixed build; for Gen 7, that means a build above 7.0.1-5035. Gen 5 is end-of-life, so replace those devices or take them off the internet.
      • Restrict management access: Until patched, disable HTTP/HTTPS and SSH management on the WAN interface (Network > Interfaces > WAN > Management). Allow management only from a dedicated admin network or a separate management VPN.
      • Lock down SSLVPN: Temporarily disable internet-facing SSLVPN, or restrict it to trusted source IP ranges. It commonly runs on TCP 4433 or a custom port.
      • Reset passwords: Force a password reset ("User must change password") for all local accounts, especially SSLVPN users and admins. This is critical on devices migrated from Gen 5/6 to Gen 7, because accounts and passwords were carried over during migration.
      • Enforce MFA: Turn on MFA (TOTP or email OTP) for all SSLVPN and admin accounts. Review current VPN sessions and terminate any that look suspicious.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Put the SSLVPN address pool in its own zone. Allow only explicitly required services from it, with no blanket "LAN Any" rule. Block RDP, SMB (445), WinRM and LDAP from the VPN pool by default.
      • Geo-IP and botnet filtering: Enable both on the firewall. Drop inbound VPN and management connections from countries you have no business with and from hosting/VPS ASNs.
      • IAM / least privilege: Replace local accounts with LDAP/RADIUS backed by MFA, and delete unused local accounts. Limit the administrator role to named individuals; no shared admin accounts.
      • Configuration hardening: Enable the account lockout policy and shorten SSLVPN and management session timeouts. Ensure syslog is forwarded to the SIEM, because on-box logs can be lost if the device crashes.
      • Configuration baseline: Back up the configuration before and after patching. Diff it for unexpected users, NAT rules or access rules.

    3. Runbook step 3

      Detection rules

      • SonicWall syslog (VPN logins): Look for SSLVPN logins by local accounts from unusual or VPS ASNs, logins outside business hours, and bursts of failed logins followed by a success. SPL sketch: index=sonicwall msg="*SSL VPN*login*" | stats count values(src) by user | where count>5
      • Management access and device restarts: Correlate admin logins on the WAN interface with unexpected firewall reboots or crashes, which may indicate exploit attempts. Also flag configuration changes that have no matching change ticket.
      • Windows events (lateral movement): Watch Event ID 4624 (logon type 3/10) and 4625 on domain controllers and servers where the source IP is in the SSLVPN pool. KQL: SecurityEvent | where EventID in (4624,4625) and IpAddress startswith "<VPN-pool-prefix>"
      • EDR / Sysmon EID 1: Look for post-exploitation patterns shortly after a VPN login:
        • vssadmin delete shadows, wmic shadowcopy
        • Impacket-style chains (cmd.exe /Q /c … 1> \\127.0.0.1\ADMIN$)
        • Installation of remote-access tools (AnyDesk, ScreenConnect)
        • Credential access against backup servers and databases
      • Zeek/Suricata: Detect internal scanning from the VPN pool (high SYN fan-out on 445/3389/135). Also flag large outbound transfers (rclone, FTP, MEGA) shortly after a VPN session starts.

    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

    An improper access control vulnerability has been identified in the SonicWall SonicOS management access, potentially leading to unauthorized resource access and in specific conditions, causing the firewall to crash. This issue affects SonicWall Firewall Gen 5 and Gen 6 devices, as well as Gen 7 devices running SonicOS 7.0.1-5035 and older versions.

    Source: cvelistv5, NVD (NIST), CISA KEV Catalog, CVE.org (MITRE), NCSC NZ (CC BY 4.0), pwn.watch

    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
    SonicWallSonicOS
    • 7.0.1-5035 and older versions
    • 6.5.4.14-109n and older versions
    • 5.9.2.14-12o and older versions
    • —
    • —
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Othersonicwallsonicos—

    Weakness classes (CWE)

    • CWE-284Improper Access Control

      Pillar

      The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.

      Entry at MITRE CWE-284

    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
    NCSC NZVulnerability in SonicWall firewalls (opens in a new tab)NCSC NZactively exploited
    ANSSI / CERT-FRLicence Ouverte 2.0, as of CERTFR-2024-ALE-011 – Vulnérabilité dans SonicWall (clôturée 2024-11-21) (opens in a new tab)cert.cyber.gouv.fractively exploited

    References & sources

    • psirt.global.sonicwall.comSonicWall advisory: CVE-2024-40766Vendor advisory, pwn-watch
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2024-40766government-resource
    • cert.atCERT.at: Erhöhte Bedrohungsaktivität gegen SonicWall Gen 7 Firewalls mit SSLVPN - Sofortmaßnahmen empfohlencert-at
    • cert.cyber.gouv.frANSSI / CERT-FR: CERTFR-2024-ALE-011 – Vulnérabilité dans SonicWall (clôturée 2024-11-21)cert-fr
    • pwn.watchpwn.watch: SonicWall SonicOS Improper Access Controlpwn-watch
    • sonicwall.comSonicWall advisory: CVE-2024-40766pwn-watch
    • NVD (NIST)NVD: CVE-2024-40766pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch

    Reanalysis & status changes

    Chronological NVD audit events for this CVE — reanalyses, CVSS updates, CPE diffs.

    1. CVE ModifiedPSIRT@sonicwall.com

      • Reference: after https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2024-0015
      • Reference: before https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2024-0015
      • Reference Type: before https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2024-0015 Types: Vendor Advisory

    2. CVE Modified134c704f-9b21-4f2e-91b3-4a467353bcc0

      • Affected: after Affected value removed. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2024/40xxx/CVE-2024-40766.json">CVE-2024-40766</a>
      • Reference: after https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-40766
      • Reference: before https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-40766
      • Reference Type: before https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-40766 Types: US Government Resource

    Linked advisories

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    Badge preview for CVE-2024-40766
    <a href="https://intel.neosec.eu/en/cve/CVE-2024-40766"><img src="https://intel.neosec.eu/badge/cve/CVE-2024-40766.svg?lang=en" alt="CVE-2024-40766 – NEOSEC Intel" height="20"></a>