CVE-2026-45078Medium· 5.5▾ SunlitSynapse CPU starvation (Denial of Service)
▾ Sunlit zone — Low / medium · no exploitation signal
impact 30.3 · likelihood 0 · exploitation 0
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Exploit-prediction probability, daily snapshots since Sep 12.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
Last analysed / modified upstream
0.1%
Local authenticated users can cause Synapse to starve other requests of CPU and lead to other requests failing, causing other users to be denied service.
Homeservers that trust all their local users are not at risk.
Update to Synapse 1.152.1 or later.
If Synapse is deployed behind a reverse proxy, the reverse proxy could be configured to limit the rate of user requests, preventing or increasing the difficulty of the attack.
If you have any questions or comments about this advisory, please email us at security at element.io.
matrix-synapse < 1.152.1Upgrade to a patched release:
matrix-synapse 1.152.1Connected by shared product, vendor, weakness, or advisory.
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