CVE-2026-36609

HIGH

Mercusys AC12G (EU) V1 - Unauthenticated Password Recovery via Static Nonce and Predictable XOR Encoding

Title source: llm

Description

Mercusys AC12G (EU) V1 router with firmware AC12G(EU)_V1_200909 uses a static authentication nonce that does not change between requests from the same source IP. Combined with the predictable XOR-based password encoding (securityEncode function), this allows an attacker to reverse captured authentication tokens to recover the plaintext password.

References (1)

Core 1

Core References

https://github.com/Tymbark7372/MERCUSYS-AC12G/blob/master/advisories/CVE-2026-36609.md

View Writeup ZIP pw:eip

Scores

CVSS v3 7.3

EPSS 0.0017

EPSS Percentile 6.1%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

CISA SSVC

Vulnrichment

Exploitation none

Automatable yes

Technical Impact total

Details

CWE

CWE-327 CWE-341

Status published

Published Jun 03, 2026

Tracked Since Jun 03, 2026