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CVE-2023-33010: Zyxel firewalls could be crashed or hijacked

CVE-2023-33010 · published 3 years ago · actively exploited

Summary

Several Zyxel firewall models and their firmware can mis‑handle certain data, letting anyone on the network cause the device to stop working or run their own code. This could disrupt your network or give attackers control of the firewall. Update the firmware to the latest version provided by Zyxel and restrict access to the firewall management interfaces.

What to do

Update zyxel atp100_firmware to version 5.36 or later.
Update zyxel atp200_firmware to version 5.36 or later.
Update zyxel atp500_firmware to version 5.36 or later.
Update zyxel atp100w_firmware to version 5.36 or later.
Update zyxel atp700_firmware to version 5.36 or later.
Update zyxel atp800_firmware to version 5.36 or later.
Update zyxel usg_flex_100_firmware to version 5.36 or later.
Update zyxel usg_flex_200_firmware to version 5.36 or later.
Update zyxel usg_flex_500_firmware to version 5.36 or later.
Update zyxel usg_flex_700_firmware to version 5.36 or later.
Update zyxel usg_flex_50w_firmware to version 5.36 or later.
Update zyxel vpn100_firmware to version 5.36 or later.
Update zyxel vpn50_firmware to version 5.36 or later.
Update zyxel vpn300_firmware to version 5.36 or later.
Update zyxel vpn1000_firmware to version 5.36 or later.
Update zyxel usg20-vpn_firmware to version 5.36 or later.
Update zyxel usg_40_firmware to version 4.73 or later.
Update zyxel usg_40w_firmware to version 4.73 or later.
Update zyxel usg_60w_firmware to version 4.73 or later.
Update zyxel usg_60_firmware to version 4.73 or later.

Affected software

Vendor	Product	Affected versions
zyxel	multiple firewalls	All versions
zyxel	atp100_firmware	>= 4.32, < 5.36 5.36 `cpe:2.3:o:zyxel:atp100_firmware::::::::`
zyxel	atp200_firmware	>= 4.32, < 5.36 5.36 `cpe:2.3:o:zyxel:atp200_firmware::::::::`
zyxel	atp500_firmware	>= 4.32, < 5.36 5.36 `cpe:2.3:o:zyxel:atp500_firmware::::::::`
zyxel	atp100w_firmware	>= 4.32, < 5.36 5.36 `cpe:2.3:o:zyxel:atp100w_firmware::::::::`
zyxel	atp700_firmware	>= 4.32, < 5.36 5.36 `cpe:2.3:o:zyxel:atp700_firmware::::::::`
zyxel	atp800_firmware	>= 4.32, < 5.36 5.36 `cpe:2.3:o:zyxel:atp800_firmware::::::::`
zyxel	usg_flex_100_firmware	>= 4.50, < 5.36 5.36 `cpe:2.3:o:zyxel:usg_flex_100_firmware::::::::`
zyxel	usg_flex_50_firmware	5.36 `cpe:2.3:o:zyxel:usg_flex_50_firmware:5.36:-::::::`
zyxel	usg_flex_200_firmware	>= 4.50, < 5.36 5.36 `cpe:2.3:o:zyxel:usg_flex_200_firmware::::::::`
zyxel	usg_flex_500_firmware	>= 4.50, < 5.36 5.36 `cpe:2.3:o:zyxel:usg_flex_500_firmware::::::::`
zyxel	usg_flex_700_firmware	>= 4.50, < 5.36 5.36 `cpe:2.3:o:zyxel:usg_flex_700_firmware::::::::`
zyxel	usg_flex_100w_firmware	5.36 `cpe:2.3:o:zyxel:usg_flex_100w_firmware:5.36:-::::::`
zyxel	usg_flex_50w_firmware	>= 4.25, < 5.36 5.36 `cpe:2.3:o:zyxel:usg_flex_50w_firmware::::::::`
zyxel	usg_20w-vpn_firmware	5.36 `cpe:2.3:o:zyxel:usg_20w-vpn_firmware:5.36:-::::::`
zyxel	vpn100_firmware	>= 4.30, < 5.36 5.36 `cpe:2.3:o:zyxel:vpn100_firmware::::::::`
zyxel	vpn50_firmware	>= 4.30, < 5.36 5.36 `cpe:2.3:o:zyxel:vpn50_firmware::::::::`
zyxel	vpn300_firmware	>= 4.30, < 5.36 5.36 `cpe:2.3:o:zyxel:vpn300_firmware::::::::`
zyxel	vpn1000_firmware	>= 4.30, < 5.36 5.36 `cpe:2.3:o:zyxel:vpn1000_firmware::::::::`
zyxel	usg20-vpn_firmware	>= 4.30, < 5.36 5.36 `cpe:2.3:o:zyxel:usg20-vpn_firmware::::::::`
zyxel	usg_40_firmware	>= 4.25, < 4.73 4.73 `cpe:2.3:o:zyxel:usg_40_firmware::::::::`
zyxel	usg_40w_firmware	>= 4.25, < 4.73 4.73 `cpe:2.3:o:zyxel:usg_40w_firmware::::::::`
zyxel	usg_60w_firmware	>= 4.25, < 4.73 4.73 `cpe:2.3:o:zyxel:usg_60w_firmware::::::::`
zyxel	usg_60_firmware	>= 4.25, < 4.73 4.73 `cpe:2.3:o:zyxel:usg_60_firmware::::::::`

Original advisory text

Zyxel Multiple Firewalls Buffer Overflow Vulnerability

Zyxel ATP, USG FLEX, USG FLEX 50(W), USG20(W)-VPN, VPN, and ZyWALL/USG firewalls contain a buffer overflow vulnerability in the ID processing function that could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions and remote code execution on an affected device.

References

https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advis... Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-... US Government Resource

Fix within

Internet-facing 3 days

and check for signs of compromise

Internal 3 days

and check for signs of compromise

Known to be exploited
Can be exploited automatically
Gives an attacker full control

Severity

9.8 Critical

Exploitation

Known exploited

Listed in the CISA KEV catalogue - exploitation confirmed in the wild.

29% chance of attack within 30 days

Type

CWE-120Classic Buffer Overflow

Timeline

Published24 May 2023

Updated6 Oct 2026

First seen6 Mar 2026

Sources

CVE-2023-33010 · CISA KEV

CVE-2023-33010 · NVD

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