How severe is CVE-2026-36609?

CVE-2026-36609 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.

Is CVE-2026-36609 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (6th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-36609?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-36609 have an EU (EUVD) identifier?

Yes. CVE-2026-36609 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-34148.

When was CVE-2026-36609 published?

CVE-2026-36609 was published on 2026-06-03 and last updated on 2026-06-17.

CVE-2026-36609

CVE-2026-36609 is a high-severity vulnerability with a CVSS 3.x base score of 7.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-327.

Key facts

Severity: High (CVSS 3.x base score 7.3)
EPSS exploit prediction: 0% (6th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-34148
Weakness: CWE-327
Published: 2026-06-03
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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. Combined with the predictable XOR-based password encoding (securityEncode function), this allows an attacker to reverse captured authentication tokens to recover the plaintext password.
How severe is CVE-2026-36609?: CVE-2026-36609 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.
Is CVE-2026-36609 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (6th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-36609?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-36609 have an EU (EUVD) identifier?: Yes. CVE-2026-36609 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-34148.
When was CVE-2026-36609 published?: CVE-2026-36609 was published on 2026-06-03 and last updated on 2026-06-17.

References

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

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