CVE-2022-34747Network attack vector

Unauthenticated code execution via UDP format string

Published Sep 6, 2022 · Updated Aug 3, 2024

Format string injection in Zyxel NAS326 firmware before V5.21(AAZF.12)C0 allows remote attackers to execute code via a crafted UDP packet. A specific firmware binary treats attacker-controlled packet data as a format string, but Zyxel has not identified the binary or function. No authentication or user interaction is required, and successful exploitation gives the attacker code execution on the NAS appliance.

CVSS severity9.8
Critical
EPSS probability1.73%
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 NAS326 firmware before V5.21(AAZF.12)C0 allows remote attackers to execute code via a crafted UDP packet. A specific firmware binary treats attacker-controlled packet data as a format string, but Zyxel has not identified the binary or function. No authentication or user interaction is required, and successful exploitation gives the attacker code execution on the NAS appliance.

The record

CVE
CVE-2022-34747
Published
Sep 6, 2022
Updated
Aug 3, 2024
Vendor
Zyxel Networks
Product
Zyxel NAS326 Firmware
Classifications
CWE-134, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 6, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=< V5.21(AAZF.12)C0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zyxel Networks · Zyxel NAS326 Firmwareversion=< V5.21(AAZF.12)C0

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8ZyxelCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-134Use of Externally-Controlled Format String
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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