How severe is CVE-2018-12291?

CVE-2018-12291 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 high, integrity none, and availability none.

Is CVE-2018-12291 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-2018-12291?

CVE-2018-12291 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2018-12291?

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-2018-12291 published?

CVE-2018-12291 was published on 2018-06-13 and last updated on 2026-06-17.

CVE-2018-12291

CVE-2018-12291 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: 2018-06-13
Last modified: 2026-06-17

Description

The on_get_missing_events function in handlers/federation.py in Matrix Synapse before 0.31.1 has a security bug in the get_missing_events federation API where event visibility rules were not applied correctly.

Frequently asked questions

What is CVE-2018-12291?: The on_get_missing_events function in handlers/federation.py in Matrix Synapse before 0.31.1 has a security bug in the get_missing_events federation API where event visibility rules were not applied correctly.
How severe is CVE-2018-12291?: CVE-2018-12291 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 high, integrity none, and availability none.
Is CVE-2018-12291 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-2018-12291?: CVE-2018-12291 affects Matrix Synapse. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2018-12291?: 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-2018-12291 published?: CVE-2018-12291 was published on 2018-06-13 and last updated on 2026-06-17.

References

Affected products (1)

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

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