Zywall USG FLEX Series & ATP Series - V5.42Patch 1 Firmware Release

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Zyxel_Melen
Zyxel_Melen Posts: 4,520 image  Zyxel Employee
Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate
edited 6:06AM in Security Gateway New Release

Zywall USG FLEX Series & ATP Series Release Note 

February 2026

Firmware Version on all models

(Click the hyperlink to find the firmware file directly)


FLEX SeriesDownload linkATP SeriesDownload link
FLEX50/USG20-VPNV5.42(ABAQ.1)C0ATP100V5.42(ABPS.1)C0
FLEX50W/USG20W-VPNV5.42(ABAR.1)C0ATP100WV5.42(ABRW.1)C0
FLEX50AXV5.42(ACGB.1)C0ATP200V5.42(ABFW.1)C0
FLEX100V5.42(ABUH.1)C0ATP500-
FLEX100WV5.42(ABWC.1)C0ATP700-
FLEX100AXV5.42(ACFN.1)C0ATP800-
FLEX200V5.42(ABUI.1)C0
FLEX500- 
FLEX700-

Note: ATP500, ATP700, ATP800, USG FLEX 500, and USG FLEX 700 are excluded for V5.42 patch 1. This exclusion is due to an issue identified during internal validation, where upgrading to ZLD 5.42 Patch 1 may fail when the device is operating in an HA configuration. Once this issue is clarified and resolved, we will proceed to release the patch after the Lunar New Year holiday.

Anyone who needs the vulnerability fix for ATP500, ATP700, ATP800, USG FLEX 500, and USG FLEX 700 without HA configuration, please download the hotfix here [Vulnerability Hotfix] CVE-2025-11730 Path Traversal Vulnerability — Zyxel Community.

New Feature and Enhancements

N/A

Bug Fix

S=Standalone mode, C=Cloud mode

Bug fixSC
[Bug Fix] eITS#260200247, 260200387, 260200388, 260200391
a. Fix: Unexpected device reboot. 		V-

Please refer to the Download Link for more details.

Zyxel Melen


Comments

  • PeterUK
    PeterUK Posts: 4,399 image  Guru Member
    250 Answers 2500 Comments Friend Collector Eighth Anniversary
    edited February 11

    Does this release include the DNS problem fix that in 542ABUI0ITS-26WK06-r117894.zip ?

    V5.42 DNS is broken with FQDN objects — Zyxel Community

    Thanks

  • Zyxel_Melen
    Zyxel_Melen Posts: 4,520 image  Zyxel Employee
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate

    Update:

    This firmware fixes the unexpected device reboot, which in most cases is caused by an abnormal FQDN object query.

    Zyxel Melen


  • Zyxel_Melen
    Zyxel_Melen Posts: 4,520 image  Zyxel Employee
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate

    Hi @PeterUK

    Yes, this is included.

    Zyxel Melen


  • Zyxel_Melen
    Zyxel_Melen Posts: 4,520 image  Zyxel Employee
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate
    edited 6:07AM

    Update:

    Note: ATP500, ATP700, ATP800, USG FLEX 500, and USG FLEX 700 are excluded for V5.42 patch 1. This exclusion is due to an issue identified during internal validation, where upgrading to ZLD 5.42 Patch 1 may fail when the device is operating in an HA configuration. Once this issue is clarified and resolved, we will proceed to release the patch after the Lunar New Year holiday.

    Anyone who needs the vulnerability fix for ATP500, ATP700, ATP800, USG FLEX 500, and USG FLEX 700 without HA configuration, please download the hotfix here [Vulnerability Hotfix] CVE-2025-11730 Path Traversal Vulnerability — Zyxel Community.

    Zyxel Melen


  • mMontana
    mMontana Posts: 1,460 image  Guru Member
    Zyxel Certified Network Administrator - Security Zyxel Certified Network Administrator - Switch 50 Answers 1000 Comments

    All dates and timings are Central European Time

    Since Tuesday 10 7:00 a USG20W-VPN is working fine.
    Since Wednesday 10 07:30 a USG20-VPN is working fine.
    I updated roughly 1h ago a USG Flex 100, next one will be updated Saturday morning.

    And the 5.42 P0 botch has confirmed that automatic update is not the best idea for my scenarios, because current scheduling options are only weekly (and not after a configurable delay from the new version availability).

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