CVE-2025-6599: Zyxel AX7501-b0 Firmware

High severity, CVSS 7.5. EPSS: 0.3% chance of exploitation in the next 30 days.

An uncontrolled resource consumption vulnerability in the web server of Zyxel DX3301-T0 firmware version 5.50(ABVY.6.3)C0 and earlier could allow an attacker to perform Slowloris‑style denial‑of‑service (DoS) attacks. Such attacks may temporarily block legitimate HTTP requests and partially disrupt access to the web management interface, while other networking services remain unaffected.

Affected products

  • Zyxel AX7501-b0 Firmware: up to and including 5.17\(abpc.6.1\)c0
  • Zyxel AX7501-b1 Firmware: up to and including 5.17\(abpc.6.1\)c0
  • Zyxel DM4200-b0 Firmware: up to and including 5.17\(acbs.1.3\)c0
  • Zyxel DX3300-t0 Firmware: up to and including 5.50\(abvy.6.3\)c0
  • Zyxel DX3300-t1 Firmware: up to and including 5.50\(abvy.6.3\)c0
  • Zyxel DX3301-t0 Firmware: up to and including 5.50\(abvy.6.3\)c0
  • Zyxel DX4510-b1 Firmware: up to and including 5.17\(abyl.9\)c0
  • Zyxel DX5401-b0 Firmware: up to and including 5.17\(abyo.7\)b2
  • Zyxel DX5401-b1 Firmware: up to and including 5.17\(abyo.7\)b2
  • Zyxel EE3301-00 Firmware: up to and including 5.63\(acmu.1.1\)c0
  • Zyxel EE5301-00 Firmware: up to and including 5.63\(acld.1.1\)c0
  • Zyxel EE6510-10 Firmware: up to and including 5.19\(acjq.3\)c0
  • Zyxel EMG3525-t50b Firmware: up to and including 5.50\(abpm.9.5\)c0
  • Zyxel EMG5523-t50b Firmware: up to and including 5.50\(abpm.9.5\)c0
  • Zyxel EMG5723-t50k Firmware: up to and including 5.50\(abom.8.6\)c0
  • Zyxel EMG6726-b10a Firmware: up to and including 5.13\(abnp.8\)c0
  • Zyxel EX3300-t0 Firmware: up to and including 5.50\(abvy.6.3\)c0; up to and including 5.50\(acdi.2.1\)c0
  • Zyxel EX3300-t1 Firmware: up to and including 5.50\(abvy.6.3\)c0
  • Zyxel EX3301-t0 Firmware: up to and including 5.50\(abvy.6.3\)c0
  • Zyxel EX3500-t0 Firmware: up to and including 5.44\(achr.4\)c0
  • Zyxel EX3501-t0 Firmware: up to and including 5.44\(achr.4\)c0
  • Zyxel EX3600-t0 Firmware: up to and including 5.70\(acif.1.2\)c0
  • Zyxel EX5401-b0 Firmware: up to and including 5.17\(abyo.7\)b2
  • Zyxel EX5401-b1 Firmware: up to and including 5.17\(abyo.7\)b2
  • Zyxel EX5501-b0 Firmware: up to and including 5.17\(abry.5.5\)c0
  • and 41 more

Published 2025-11-18. Last modified 2026-06-17.