Security Resilience

CVE-2020-8515

RCE in Draytek Vigor300B Firmware 1.3.3 … 1.4.4

CISA KEVActive ExploitationEUVD ExploitedPublic PoCRCECommand Injection
Published
01 February 2020
Modified
07 November 2025
KEV Added
03 November 2021
Patch / advisory
View advisory
CVSS Score v3.1 9.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.99 100.0th percentile
Risk Priority 97 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2020-8515 is a critical-severity OS Command Injection (CWE-78) vulnerability in Draytek Vigor300B Firmware. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique NTDS (T1003.003); ranked in the top 0.0% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2020-8515 is an unauthenticated remote code execution vulnerability in the web management interface of DrayTek Vigor2960 1.3.1_Beta, Vigor3900 1.4.4_Beta, and Vigor300B 1.3.3_Beta, 1.4.2.1_Beta, and 1.4.4_Beta devices. The flaw stems from improper handling of shell metacharacters passed to the cgi-bin/mainfunction.cgi endpoint, enabling command injection and resulting in root-level code execution on the affected routers. It is tracked under CWE-78 and carries a CVSS 3.1 base score of 9.8.

An attacker with network access to the management interface can send a crafted HTTP request containing shell metacharacters to the vulnerable CGI script. Because no authentication is required, successful exploitation grants immediate root privileges, allowing arbitrary command execution, configuration changes, or full device compromise.

DrayTek's security advisory states that the issue has been resolved in firmware version 1.5.1 for the Vigor3900, Vigor2960, and Vigor300B series; administrators are advised to apply the update promptly to eliminate the injection vector. Public exploit code and technical write-ups have been published, confirming the attack's practicality against unpatched beta releases.

OWASP Top 10 for Web (2025)

A05:2025 Injection

EU & UK References

Vulnerability Data

DrayTek Vigor2960 1.3.1_Beta, Vigor3900 1.4.4_Beta, and Vigor300B 1.3.3_Beta, 1.4.2.1_Beta, and 1.4.4_Beta devices allow remote code execution as root (without authentication) via shell metacharacters to the cgi-bin/mainfunction.cgi URI. This issue has been fixed in Vigor3900/2960/300B v1.5.1.

CWE(s)
CWE-78
KEV Date Added
03 November 2021

Related Threats

Threat-Actor AttributionAI

Microsoft Corp. (Salesforce / Slack engineer recruitment claims)
Potential for China Cyber Response to Heightened U.S.–China Tensions | CISA
APT1 (G0006)
Potential for China Cyber Response to Heightened U.S.–China Tensions | CISA
Deep Panda (G0009)
Potential for China Cyber Response to Heightened U.S.–China Tensions | CISA
APT3 (G0022)
Potential for China Cyber Response to Heightened U.S.–China Tensions | CISA
Winnti Group (G0044)
Potential for China Cyber Response to Heightened U.S.–China Tensions | CISA
menuPass (G0045)
Potential for China Cyber Response to Heightened U.S.–China Tensions | CISA
Leviathan (G0065)
Potential for China Cyber Response to Heightened U.S.–China Tensions | CISA
APT19 (G0073)
Potential for China Cyber Response to Heightened U.S.–China Tensions | CISA
APT41 (G0096)
Potential for China Cyber Response to Heightened U.S.–China Tensions | CISA
AnonOps
Potential for China Cyber Response to Heightened U.S.–China Tensions | CISA
The Magic
People’s Republic of China State-Sponsored Cyber Actors Exploit Network Providers and Devices | CISA

MITRE ATT&CK Enterprise Techniques

T1003.003 NTDS Credential Access
Adversaries may attempt to access or create a copy of the Active Directory domain database in order to steal credential information, as well as obtain other information about domain members such as devices, users, and access rights.
attack.mitre.org →
T1007 System Service Discovery Discovery
Adversaries may try to gather information about registered local system services.
attack.mitre.org →
T1010 Application Window Discovery Discovery
Adversaries may attempt to get a listing of open application windows.
attack.mitre.org →
T1021.004 SSH Lateral Movement
Adversaries may use [Valid Accounts](https://attack.
attack.mitre.org →
T1021.008 Direct Cloud VM Connections Lateral Movement
Adversaries may leverage [Valid Accounts](https://attack.
attack.mitre.org →
T1027.001 Binary Padding Stealth
Adversaries may use binary padding to add junk data and change the on-disk representation of malware.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2020-15415Same product: Draytek Vigor2960both on KEV
CVE-2024-12987Same product: Draytek Vigor2960both on KEV
CVE-2024-12986Same product: Draytek Vigor2960
CVE-2024-45888Same product: Draytek Vigor3900
CVE-2024-51244Same product: Draytek Vigor3900
CVE-2024-45887Same product: Draytek Vigor3900
CVE-2024-45889Same product: Draytek Vigor3900
CVE-2024-45891Same product: Draytek Vigor3900
CVE-2024-51251Same product: Draytek Vigor3900
CVE-2024-51249Same product: Draytek Vigor3900

Affected Assets

draytek
vigor2960 firmware
1.3.1
draytek
vigor300b firmware
1.3.3, 1.4.2.1, 1.4.4
draytek
vigor3900 firmware
1.4.4

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V1.2.5
  • V1.2.8

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SC-27 Platform-independent Applications
addresses: CWE-78

Platform-independent apps typically execute inside a managed runtime or sandbox that restricts direct OS command execution, reducing the ability to exploit OS command injection.

SI-10 Information Input Validation
addresses: CWE-78

Validates inputs to block special elements that would alter OS command execution.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
blocks

PR.PS-06's SDLC practices directly require secure coding and input handling that blocks command-injection defects, yet the single broad outcome leaves many specific neutralization vectors and verification gaps unaddressed.

PR.PS-02 partial match
blocks

Routine patching/maintenance can remediate known command-injection CVEs in dependencies (partial forward) but does nothing to stop developers from introducing improper neutralization in custom code (none reverse).

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.14 Information transfer partial match
removes
A.5.15 Access control partial match
removes
A.5.16 Identity management partial match
removes
A.5.17 Authentication information partial match
removes
A.5.18 Access rights partial match
removes
A.8.10 Information deletion partial match
removes

References