CriticalCVE-2021-32030

    ASUS Routers Improper Authentication Vulnerability (CVE-2021-32030)

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

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    What is affected, what to do

    The administrator application on ASUS GT-AC2900 devices before 3.0.0.4.386.42643 and Lyra Mini before 3.0.0.4_384_46630 allows authentication bypass when processing remote input from an unauthenticated user, leading to unauthorized access to the administrator interface. This relates to handle_request in router/httpd/httpd.c and auth_check in web_hook.o.

    The vulnerability is being actively exploited; treat it as a priority. Update ASUS Lyra Mini Firmware to version 3.0.0.4.384.46630, ASUS Gt-ac2900 Firmware to version 3.0.0.4.386.42643. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • ASUS Lyra Mini Firmware lt *..3.0.0.4.384.46630
    • ASUS Gt-ac2900 Firmware lt *..3.0.0.4.386.42643
    Fixed in
    • ASUS Lyra Mini Firmware 3.0.0.4.384.46630
    • ASUS Gt-ac2900 Firmware 3.0.0.4.386.42643

    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

    99.39 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.94

    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
    228.90 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 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.

    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
    99.39 %
    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
    99.94
    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 · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 6 June 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-287

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is reachable over the network without authentication or user interaction and hands over full admin control. It sits among the CVEs most likely to be exploited of all. Its late KEV listing reflects current campaigns that mass-compromise SOHO routers to plant persistent backdoors and turn the devices into proxy or botnet infrastructure. CISA does not flag ransomware use, so the real risk is espionage, traffic interception and abuse of your IP reputation. Typical victims are branch sites, small offices and home workers. Treat any affected device with WAN admin exposed as critical and fix it within 24 hours. LAN-only exposure is high priority, and if you have no ASUS estate, an inventory check is all that's needed.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Find the devices: Locate every ASUS GT-AC2900 and ASUS Lyra Mini, including branch offices, labs and remote workers' home setups with corporate access. Use DHCP leases, MAC OUI lookups and outreach to business units. These consumer boxes rarely appear in the CMDB.

      • Kill WAN administration now: Set "Administration → System → Enable Web Access from WAN = No", which is the vendor-stated mitigation. ASUS typically exposes the WAN admin UI on 8443/HTTPS or 8080/HTTP, but confirm the actual port in the config. Verify from outside with a port scan that it is closed.

      • Patch: Upgrade GT-AC2900 to 3.0.0.4.386.42643 or later and Lyra Mini to 3.0.0.4.384.46630 or later (written 3.0.0.4_384_46630 in the advisory). Download only from the official ASUS support site and verify checksums.

      • Retire EoL units: CISA notes that affected products may be end-of-life or end-of-service, and those units will never get a fix. Schedule replacement with supported hardware and keep them strictly isolated until then.

      • Assume compromise where the UI was internet-facing: Check the config for:

        • SSH enabled, especially on odd high ports
        • authorised SSH keys
        • changed DNS servers
        • port forwards
        • new accounts

        A firmware upgrade does not remove changes persisted in NVRAM. If anything looks off, factory-reset the device, reflash the firmware and reconfigure it by hand. Do not restore old config backups.

      • Rotate secrets: Change the router admin password, Wi-Fi PSKs, and any VPN or PPPoE credentials stored on the device.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Never let a consumer router act as the perimeter for corporate assets. Put it behind a managed firewall, or force corporate endpoints behind it onto an always-on VPN tunnel.
      • Perimeter filtering: On the upstream firewall or ISP edge, drop inbound traffic to the router's WAN IPs on TCP 80/443/8080/8443 and any unneeded service ports, including SSH and Telnet. If remote admin is unavoidable, restrict it to fixed admin source IPs.
      • IPS signature: Deploy a Suricata rule that flags requests to the router UI with an empty or null asus_token cookie, for example alert http any any -> $ROUTER_NET any (msg:"CVE-2021-32030 ASUS asus_token null bypass"; http.cookie; content:"asus_token="; pcre:"/asus_token=(%00|\x00|;|$)/"; sid:9203201;). Run it in alert mode before blocking.
      • Configuration hardening: Disable AiCloud, UPnP, WPS, and WAN-side SSH and Telnet. Allow the web UI over HTTPS from the LAN only, and keep the management VLAN separate from user Wi-Fi.
      • Governance and lifecycle: Adopt a procurement rule that bans consumer network gear without guaranteed security support from business use, in line with NIS2 Art. 21 supply-chain security.

    3. Runbook step 3

      Detection rules

      • Network telemetry (Zeek/firewall): Alert on inbound internet connections to the router's WAN admin port from unknown sources. KQL: CommonSecurityLog | where DestinationIP in (router_wan_ips) and DestinationPort in (8080,8443,80,443) and SourceIP !in (admin_ips).
      • HTTP inspection (Suricata/proxy): Look for requests to *.cgi, /appGet.cgi or /apply.cgi with no preceding successful login.cgi and an empty or null asus_token. Sigma shape: selection: cs-cookie|contains: 'asus_token=%00', or asus_token= at the end of the cookie.
      • Router syslog (forward to central syslog): Watch for config changes, dropbear/sshd starting, new port forwards, DNS changes, or firmware upgrades outside maintenance windows.
      • Persistence indicators: An internet-reachable SSH service on the router WAN IP, especially on a high non-standard TCP port. Public reporting on 2025 campaigns cites TCP 53282 as one example. Schedule recurring external scans of your own WAN IPs, for example with Shodan Monitor or an Nmap job.
      • Outbound anomalies: Flag the router WAN IP initiating connections to unfamiliar destinations, or DHCP clients receiving unexpected DNS resolvers. Either points to proxy or botnet abuse or to DNS hijacking.

    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

    The administrator application on ASUS GT-AC2900 devices before 3.0.0.4.386.42643 and Lyra Mini before 3.0.0.4_384_46630 allows authentication bypass when processing remote input from an unauthenticated user, leading to unauthorized access to the administrator interface. This relates to handle_request in router/httpd/httpd.c and auth_check in web_hook.o. An attacker-supplied value of '\0' matches the device's default value of '\0' in some situations. Note: All versions of Lyra Mini and earlier which are unsupported (End-of-Life, EOL) are also affected by this vulnerability, Consumers can mitigate this vulnerability by disabling the remote access features from WAN.

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

    Vendors and products

    Affected operating systems

    Affected operating systems
    Otherasusgt-ac2900_firmware—
    Otherasuslyra_mini_firmware—

    Weakness classes (CWE)

    • CWE-287Improper Authentication

      Class

      When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.

      Entry at MITRE CWE-287

    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
    Reference tagged as exploitgithub.com (opens in a new tab)PoC (publicly reported)reported, not verified—

    References & sources

    • asus.comNetworking-IoT-Servers/WiFi-Routers/ASUS-Gaming-Routers/RT-AC29…Product
    • github.comatredispartners/advisories/blob/master/ATREDIS-2020-0010.mdBroken link, Exploit, Third-party advisory
    • atredis.comblog/2021/4/30/asus-authentication-bypassExploit
    • asus.comASUS advisory: ASUS RoutersProduct, pwn-watch
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2021-32030government-resource, US government resource
    • pwn.watchpwn.watch: ASUS Routers: Routers Improper Authentication Vulnerabilitypwn-watch
    • asus.comASUS advisory: ASUS Routerspwn-watch
    • NVD (NIST)NVD: CVE-2021-32030pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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