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Vulnerabilities

Vulnerability · CVE-2026-36609

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.

Published Jun 3, 2026 · catalog updated Jul 22, 2026 · Mercusys AC12G (EU) V1

Check if you run it

No confirmed exploitation is on record for CVE-2026-36609. EPSS is 0.23%. Act only if a listed version of Mercusys AC12G (EU) V1 is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Mercusys AC12G (EU) V1).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.23%
Remediation
Not established
Affected products
See sources for product scope

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.

No affected version ranges are stored yet. Use the vendor advisory before you decide this record does not apply.

How to fix CVE-2026-36609

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-36609. EPSS is 0.23%. Act only if a listed version of Mercusys AC12G (EU) V1 is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-327: Use of a Broken or Risky Cryptographic Algorithm; CWE-341. EPSS 0.23%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Jun 3, 2026 · NIST NVD

    Detected

    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.

  2. Jul 22, 2026 · NIST NVD

    Updated

    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.

Sources

  • CVE.orgVulnerability recordCVE-2026-36609

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-36609

    30-day exploitation probability 0.2%

    first.org
  • NIST NVDVulnerability recordCVE-2026-36609

    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 revers

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.