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CVE-2018-12291 High

Matrix Synapse Security Filtering Flaw

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.

Exploit probability 1.8%
Published July 2, 2026
Required by Not available
Last source change July 6, 2026

02 / AFFECTED SOFTWARE

Affected packages

Unknown Unknown

88 explicit affected versions

PyPI matrix-synapse
PyPI matrix-synapse

03 / CONNECTIONS

Connected vulnerabilities

04 / EVIDENCE

Source records

Open Source Vulnerabilities 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.

View original source
Open Source Vulnerabilities GHSA-v8wm-g9f2-xjv4

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.

View original source
Open Source Vulnerabilities PYSEC-2026-664

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.

View original source

05 / REFERENCES

Further evidence