CVE-2023-31447Network attack vector

Unauthenticated code execution via login format string

Published Aug 21, 2023 · Updated Oct 7, 2024

Format string injection in user_login.cgi in DrayTek Vigor 2620 before 3.9.8.4 allows remote attackers to execute arbitrary code. The login handler processes attacker-controlled payload data as a format string, permitting memory writes that alter code-segment content and place shellcode. No authentication or user interaction is required; successful exploitation runs code on the router, while less-capable payloads can reboot it.

CVSS severity9.8
Critical
EPSS probability0.94%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Format string injection in user_login.cgi in DrayTek Vigor 2620 before 3.9.8.4 allows remote attackers to execute arbitrary code. The login handler processes attacker-controlled payload data as a format string, permitting memory writes that alter code-segment content and place shellcode. No authentication or user interaction is required; successful exploitation runs code on the router, while less-capable payloads can reboot it.

The record

CVE
CVE-2023-31447
Published
Aug 21, 2023
Updated
Oct 7, 2024
Vendor
DrayTek
Product
Vigor 2620
Classifications
CWE-94, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 21, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 7, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <3.9.8.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

DrayTek · Vigor 2620version=0 <3.9.8.4

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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