CVE-2023-33011

OS command execution via crafted PPPoE configuration

Published Jul 17, 2023 · Updated Nov 7, 2024

Format string injection in Zyxel firewall firmware through 5.36 Patch 2 allows remote attackers on the LAN to execute OS commands. The PPPoE configuration handler treats attacker-controlled configuration text as a format string, enabling command execution. Exploitation requires LAN access and cloud management mode; successful attacks execute commands with the appliance's operating-system privileges.

CVSS severity8.8
High
EPSS probability0.34%
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 Zyxel firewall firmware through 5.36 Patch 2 allows remote attackers on the LAN to execute OS commands. The PPPoE configuration handler treats attacker-controlled configuration text as a format string, enabling command execution. Exploitation requires LAN access and cloud management mode; successful attacks execute commands with the appliance's operating-system privileges.

The record

CVE
CVE-2023-33011
Published
Jul 17, 2023
Updated
Nov 7, 2024
Vendor
Zyxel Networks
Product
Zyxel USG FLEX 50W Firmware
Classifications
CWE-134, T1059
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 17, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 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=5.10 <=5.36_patch_2
  2. Affected versionversion=5.10 through 5.36 Patch 2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Zyxel Networks · Zyxel USG FLEX 50W Firmwareversion=5.10 <=5.36_patch_2; version=5.10 through 5.36 Patch 2
Zyxel Networks · USG20W-VPN Firmwareversion=5.10 <=5.36_patch_2
Zyxel Networks · Zyxel ATP Series Firmwareversion=5.10 through 5.36 Patch 2
Zyxel Networks · Zyxel USG20(W)-VPN Series Firmwareversion=5.10 through 5.36 Patch 2
Zyxel Networks · Zyxel VPN Series Firmwareversion=5.00 <=5.36_patch_2; version=5.00 through 5.36 Patch 2
Zyxel Networks · Zyxel ATP100 Firmwareversion=5.10 <=5.36_patch_2
Zyxel Networks · Zyxel USG FLEX Series Firmwareversion=5.0.0 <=5.36_patch_2; version=5.00 through 5.36 Patch 2

Published CVSS scores

8.8Zyxel CorporationCVSS:3.1/AV:A/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.

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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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-134Use of Externally-Controlled Format String
T1059Command and Scripting Interpreter

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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