CVE-2024-6343Network attack vector

Administrator-triggered service interruption via CGI buffer overflow

Published Sep 3, 2024 · Updated Sep 3, 2024

Buffer overflow in Zyxel ZLD firewall CGI software allows remote authenticated users to interrupt affected firewall operation. The CGI program copies crafted HTTP-request input without checking that it fits the destination buffer, but Zyxel has not identified the endpoint or copy operation. Affected versions are ATP 4.32 through 5.38, USG FLEX 4.50 through 5.38, and USG FLEX 50 and USG20(W)-VPN 4.16 through 5.38; exploitation requires administrator access, and the vendor does not disclose whether interruption is a crash, hang, or reboot.

CVSS severity4.9
Medium
EPSS probability0.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in Zyxel ZLD firewall CGI software allows remote authenticated users to interrupt affected firewall operation. The CGI program copies crafted HTTP-request input without checking that it fits the destination buffer, but Zyxel has not identified the endpoint or copy operation. Affected versions are ATP 4.32 through 5.38, USG FLEX 4.50 through 5.38, and USG FLEX 50 and USG20(W)-VPN 4.16 through 5.38; exploitation requires administrator access, and the vendor does not disclose whether interruption is a crash, hang, or reboot.

The record

CVE
CVE-2024-6343
Published
Sep 3, 2024
Updated
Sep 3, 2024
Vendor
Zyxel Networks
Product
USG20(W)-VPN Series
Classifications
CWE-120, T1499.004
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Sep 3, 2024CVE publishedPublication date reported by the CVE source.
  2. Sep 3, 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=versions V4.16 through V5.38

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Zyxel Networks · USG20(W)-VPN Seriesversion=versions V4.16 through V5.38
Zyxel Networks · USG FLEX 50 Seriesversion=versions V4.16 through V5.38
Zyxel Networks · ATP Seriesversion=versions V4.32 through V5.38
Zyxel Networks · USG FLEX Seriesversion=versions V4.50 through V5.38

Published CVSS scores

4.9Zyxel CorporationCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/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.

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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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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