CriticalCVE-2023-28461

    Array Networks AG and vxAG ArrayOS Missing Authentication for Critical Function Vulnerability (CVE-2023-28461)

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

    What is affected, what to do

    Array Networks Array AG Series and vxAG (9.4.0.481 and earlier) allow remote code execution. An attacker can browse the filesystem on the SSL VPN gateway using a flags attribute in an HTTP header without authentication.

    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
    • Arraynetworks Arrayos Ag lte *..9.4.0.481

    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: pwn.watch, CVE.org

    68.1 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.33

    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
    255.30 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.

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    actively exploited
    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.

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    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“.

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    68.1 %
    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
    99.33
    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 reachable over the network with no authentication and no user interaction, and it gives an attacker file read and code execution on a perimeter device. That makes it an ideal initial-access vector into the internal network. CISA explicitly flags known use in ransomware campaigns, and its exploitation likelihood is among the very highest of any CVE. Typical targets are organisations relying on Array SSL VPNs for remote access, including manufacturing, public sector and critical-infrastructure operators. Treat every internet-exposed instance on ArrayOS AG 9.4.0.481 or earlier as an emergency change, and remediate internally reachable instances within days.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Enumerate every Array Networks AG and vxAG appliance (physical and virtual) running ArrayOS AG and confirm the exact firmware build. Versions 9.4.0.481 and earlier are affected. Treat any internet-facing unit on these builds as potentially compromised until proven otherwise.
      • Patch: Upgrade to a fixed ArrayOS AG release newer than 9.4.0.481. The patch is available from the vendor — look up the exact version in the Array Networks advisory. Before upgrading, take a config snapshot and a forensic copy of the logs so evidence is not overwritten.
      • Reduce exposure: If you cannot upgrade immediately, restrict the SSL VPN / web portal listener (typically TCP/443) at the perimeter firewall to known source ranges, or take the gateway offline temporarily. Never expose the management interface to the internet.
      • Rotate credentials: The flaw allows unauthenticated local file reads, so rotate every secret stored on or passing through the gateway. This covers local admin accounts, LDAP/RADIUS bind accounts, portal certificates and private keys, and VPN user passwords.
      • Compromise assessment: Review gateway logs going back several months (see Detection). If you find signs of exploitation, trigger incident response, assess the NIS2 early-warning obligation (within 24 h), and rebuild the appliance rather than just patching it.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Run the gateway in a dedicated DMZ. Restrict its egress with an allowlist to the required destinations only (AAA servers, NTP, DNS, syslog), and block everything else to stop reverse shells and exfiltration.
      • East-west control: Limit traffic from VPN client pools and the gateway itself to the internal services users actually need. Be especially selective with SMB, RDP, WinRM and LDAP towards domain controllers.
      • WAF/IPS: Put a reverse proxy or IPS in front of the portal and drop requests that carry anomalous headers with a "flags" attribute. Also block path-traversal patterns (../, %2e%2e) and requests for system paths (/etc/, /proc/). Enable your IPS vendor's signatures for CVE-2023-28461.
      • IAM/least privilege: Reduce directory bind accounts to minimal read rights. Enforce MFA for all VPN users so that leaked passwords are not directly usable.
      • Configuration hardening: Disable portal features you do not need (e.g. web resources, file shares exposed via the portal) and check the config against the vendor's hardening guidance. Forward syslog to the SIEM so that tampering with local logs stays detectable.

    3. Runbook step 3

      Detection rules

      • Gateway web/access logs: Look for unauthenticated requests (no valid session) to unusual URLs that returned HTTP 200 with abnormally large response sizes, and for headers containing a "flags" attribute. Example (SPL): index=vpn sourcetype=array:ag status=200 NOT session_id=* | stats count by src_ip, uri_path
      • Network telemetry (Zeek/Suricata): Alert on outbound connections from the gateway to unknown external IPs or unusual ports, which can indicate a reverse shell or tool download. Example (Zeek conn.log): id.orig_h == <AG-IP> and not id.resp_h in allowlist
      • Lateral movement: Watch for new logons from the VPN pool or gateway address range to domain controllers and servers. Focus on Windows Event ID 4624 (logon type 3/10) involving the gateway's service accounts, and on clusters of 4625 failures. Sigma shape: logsource: windows/security; selection: EventID 4624, IpAddress|cidr: <VPN-pool>, TargetUserName: <svc-ag>
      • Configuration changes: Alert on new local admin accounts, modified portal configuration or unexpected reboots in the gateway syslog. Diff the running config against a known-good baseline (hash compare).
      • Credential abuse: Correlate VPN logins at atypical hours, from new geolocations, or concurrent sessions on a single account. These patterns point to stolen credentials being reused.

    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

    Array Networks Array AG Series and vxAG (9.4.0.481 and earlier) allow remote code execution. An attacker can browse the filesystem on the SSL VPN gateway using a flags attribute in an HTTP header without authentication. The product could then be exploited through a vulnerable URL. The 2023-03-09 vendor advisory stated "a new Array AG release with the fix will be available soon."

    Source: pwn.watch, CISA KEV Catalog, cvelistv5, NVD (NIST), CVE.org (MITRE)

    Vendors and products

    Affected operating systems

    Affected operating systems
    Otherarraynetworksarrayos_ag—

    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

    • support.arraynetworks.netArray Networks advisory: CVE-2023-28461pwn-watch
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2023-28461government-resource
    • pwn.watchpwn.watch: Array Networks AG and vxAG ArrayOS Missing Authentication for Critical Functionpwn-watch
    • NVD (NIST)NVD: CVE-2023-28461pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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