CriticalCVE-2020-15415

    DrayTek Multiple Vigor Routers OS Command Injection Vulnerability (CVE-2020-15415)

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

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    What is affected, what to do

    This vulnerability allows an attacker to perform remote code execution (RCE) on DrayTek Vigor3900, Vigor2960, and Vigor300B devices prior to version 1.5.1 via OS command injection. The attack can be executed without authentication, enabling the execution of arbitrary code on the device. The exploit is actively used in the field and documented in ransomware campaigns since 2024. Affected organizations should immediately update to firmware version 1.5.1 to mitigate the risk.

    The vulnerability is being actively exploited; treat it as a priority. Update DrayTek Vigor3900 Firmware to version 1.5.1, DrayTek Vigor2960 Firmware to version 1.5.1, DrayTek Vigor300b Firmware to version 1.5.1. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • DrayTek Vigor3900 Firmware lt *..1.5.1
    • DrayTek Vigor2960 Firmware lt *..1.5.1
    • DrayTek Vigor300b Firmware lt *..1.5.1
    Fixed in
    • DrayTek Vigor3900 Firmware 1.5.1
    • DrayTek Vigor2960 Firmware 1.5.1
    • DrayTek Vigor300b Firmware 1.5.1

    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

    84.5 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.70

    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
    228.52 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“.

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    84.5 %
    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
    99.70
    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 4 October 2024
    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-78

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw gives unauthenticated, network-reachable remote code execution on a perimeter device with no user interaction. The Exploit Prediction Scoring System ranks it among the CVEs most likely to be exploited. DrayTek routers are a staple target for botnets and for operators who use edge devices as proxies, as footholds for lateral movement, or to harvest VPN credentials. The late KEV listing reflects continued mass exploitation of unpatched and end-of-life units still in service. CISA currently reports no known ransomware use. Rate any unit with an internet-exposed web UI as critical, fix within 24 h. Rate internally reachable units as high, to be patched or replaced in the next maintenance window. For NIS2 and KRITIS entities, a confirmed compromise of a perimeter device should be assessed as a potentially reportable incident.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Identify every DrayTek Vigor3900, Vigor2960 and Vigor300B in your estate. Use the CMDB, Shodan/Censys lookups of your own public ranges, and an internal scan for the DrayTek web UI. Record the firmware version on each device.
      • Upgrade firmware: Upgrade all affected units to firmware 1.5.1 or later. First check whether the model is end-of-life with the vendor. If a device no longer receives updates, schedule its replacement and treat the hardening in "Mitigation layers" as mandatory until then.
      • Pull the management UI off the internet: Immediately disable WAN-side web administration (HTTP/HTTPS, usually TCP 80/443 or a custom admin port) or restrict it to fixed admin source IPs.
      • Hunt for compromise: If a device's web UI was internet-reachable before patching, diff its config, user accounts, VPN profiles, port forwards, DNS settings and scheduled tasks against a known-good backup. Where CLI access allows, capture unknown processes and files (e.g. in /tmp).
      • Rotate secrets: After patching a previously exposed unit, rotate admin passwords, VPN PSKs, certificates and any RADIUS, LDAP or SNMP secrets stored on the device. If compromise is suspected, factory-reset the device and rebuild the config by hand rather than restoring a backup.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Make the management UI reachable only from a dedicated admin VLAN or jump host. ACL-block user and guest VLANs from the router's management IP. The flaw needs no authentication, so internal attackers can exploit it too.
      • IPS/WAF rule: At the perimeter IPS, or at a reverse proxy if the UI must be published, block requests to /cgi-bin/mainfunction.cgi/cvmcfgupload, especially multipart uploads carrying Content-Type: text/x-python-script. Suricata example: alert http any any -> $HOME_NET any (msg:"CVE-2020-15415 DrayTek cvmcfgupload"; flow:to_server; http.uri; content:"/cgi-bin/mainfunction.cgi/cvmcfgupload"; nocase; http.request_body; content:"text/x-python-script"; nocase; sid:<local SID>; rev:1;)
      • Egress filtering for the device itself: Limit router-originated traffic to what it needs: NTP, DNS to internal resolvers, and the vendor firmware servers. This stops wget/curl payload staging and C2 call-outs.
      • Remote admin hardening: Administer the router through a separate MFA-protected VPN that does not terminate on the affected device. Disable Telnet, and disable WAN-side SSH and SNMP.
      • Lifecycle: Following CISA guidance, discontinue end-of-life models. Until they are replaced, treat them as untrusted and add monitoring on the VPN tunnels and routing they carry.

    3. Runbook step 3

      Detection rules

      • Perimeter HTTP telemetry (Zeek http.log / proxy): Look for requests to cvmcfgupload. SPL example: index=zeek sourcetype=zeek_http uri="*mainfunction.cgi/cvmcfgupload*" | stats count by id.orig_h, id.resp_h, user_agent. Treat any internet-sourced hit as an exploitation attempt.
      • Shell metacharacters in the upload filename: In IPS payload logs or PCAP, look for filename= values containing ;, |, `, $( or && alongside text/x-python-script. A Sigma starting point is logsource: category: webserver with cs-uri-stem|contains: 'cvmcfgupload'.
      • Router-originated connections (NetFlow/Zeek conn.log): Flag outbound sessions sourced from the router's management or WAN IP to unknown destinations on TCP 80/443/8080 or odd high ports. Also flag DNS lookups by the router for newly registered domains. KQL shape: CommonSecurityLog | where SourceIP in (draytek_ips) and DestinationIP !in (allowed) | summarize count() by DestinationIP, DestinationPort.
      • Router syslog (forward to SIEM): Watch for unexpected config changes, new admin accounts, new VPN profiles, reboots outside maintenance windows, and admin logins from unfamiliar IPs. If syslog forwarding is not enabled, turn it on now.
      • Lateral movement: Internal scanning or connection attempts from the router's LAN IP to servers (SMB, RDP, SSH) indicate the device is being used as a pivot.

    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

    On DrayTek Vigor3900, Vigor2960, and Vigor300B devices before 1.5.1, cgi-bin/mainfunction.cgi/cvmcfgupload allows remote command execution via shell metacharacters in a filename when the text/x-python-script content type is used, a different issue than CVE-2020-14472.

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

    Vendors and products

    Affected operating systems

    Affected operating systems
    Otherdraytekvigor2960_firmware—
    Otherdraytekvigor300b_firmware—
    Otherdraytekvigor3900_firmware—

    Weakness classes (CWE)

    • CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

      Base

      The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

      Entry at MITRE CWE-78

    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

    • draytek.comabout/security-advisoryx_refsource_MISC, Vendor advisory
    • github.comCLP-team/Vigor-Commond-Injectionx_refsource_MISC, Exploit
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2020-15415government-resource, US government resource
    • pwn.watchpwn.watch: DrayTek Multiple Vigor Routers OS Command Injectionpwn-watch
    • draytek.comDrayTek advisory: CVE-2020-15415pwn-watch
    • NVD (NIST)NVD: CVE-2020-15415pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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