How severe is CVE-2018-12423?

CVE-2018-12423 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2018-12423 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-12423?

CVE-2018-12423 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2018-12423?

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.

When was CVE-2018-12423 published?

CVE-2018-12423 was published on 2018-06-14 and last updated on 2026-06-17.

CVE-2018-12423

CVE-2018-12423 is a high-severity vulnerability in Matrix Synapse with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Matrix Synapse
Published: 2018-06-14
Last modified: 2026-06-17

Description

In Synapse before 0.31.2, unauthorised users can hijack rooms when there is no m.room.power_levels event in force.

Frequently asked questions

What is CVE-2018-12423?: In Synapse before 0.31.2, unauthorised users can hijack rooms when there is no m.room.power_levels event in force.
How severe is CVE-2018-12423?: CVE-2018-12423 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2018-12423 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-12423?: CVE-2018-12423 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2018-12423?: 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.
When was CVE-2018-12423 published?: CVE-2018-12423 was published on 2018-06-14 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*

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