What’s Vulnerable › Vulnerabilities

CVE-2019-15802

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2019-11-14 · updated 2026-06-17
• Weakness: CWE-798

Description

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. The firmware hashes and encrypts passwords using a hardcoded cryptographic key in sal_util_str_encrypt() in libsal.so.0.0. The parameters (salt, IV, and key data) are used to encrypt and decrypt all passwords using AES256 in CBC mode. With the parameters known, all previously encrypted passwords can be decrypted. This includes the passwords that are part of configuration backups or otherwise embedded as part of the firmware.

Affected products

• Zyxel GS1900-10HP firmware: before 2.50\(aazi.0\)c0 — fixed in 2.50\(aazi.0\)c0
• Zyxel GS1900-16 firmware: before 2.50\(aahj.0\)c0 — fixed in 2.50\(aahj.0\)c0
• Zyxel GS1900-24 firmware: before 2.50\(aahl.0\)c0 — fixed in 2.50\(aahl.0\)c0
• Zyxel GS1900-24E firmware: before 2.50\(aahk.0\)c0 — fixed in 2.50\(aahk.0\)c0
• Zyxel Gs1900-24Hp Firmware: before 2.50\(aahm.0\)c0 — fixed in 2.50\(aahm.0\)c0
• Zyxel GS1900-48 firmware: before 2.50\(aahn.0\)c0 — fixed in 2.50\(aahn.0\)c0
• Zyxel Gs1900-48Hp Firmware: before 2.50\(aaho.0\)c0 — fixed in 2.50\(aaho.0\)c0
• Zyxel GS1900-8 firmware: before 2.50\(aahh.0\)c0 — fixed in 2.50\(aahh.0\)c0
• Zyxel GS1900-8HP firmware: before 2.50\(aahi.0\)c0 — fixed in 2.50\(aahi.0\)c0

How to fix

Upgrade to a fixed version: Zyxel GS1900-10HP firmware 2.50\(aazi.0\)c0; Zyxel GS1900-16 firmware 2.50\(aahj.0\)c0; Zyxel GS1900-24 firmware 2.50\(aahl.0\)c0; Zyxel GS1900-24E firmware 2.50\(aahk.0\)c0; Zyxel Gs1900-24Hp Firmware 2.50\(aahm.0\)c0; Zyxel GS1900-48 firmware 2.50\(aahn.0\)c0; Zyxel Gs1900-48Hp Firmware 2.50\(aaho.0\)c0; Zyxel GS1900-8 firmware 2.50\(aahh.0\)c0; Zyxel GS1900-8HP firmware 2.50\(aahi.0\)c0. Check the vendor advisory for mitigations.

References

• https://jasper.la/exploring-zyxel-gs1900-firmware-with-ghidra.html
• https://www.zyxel.com/support/gs1900-switch-vulnerabilities.shtml
• https://jasper.la/exploring-zyxel-gs1900-firmware-with-ghidra.html
• https://www.zyxel.com/support/gs1900-switch-vulnerabilities.shtml

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