What is CVE-2026-45076?

CVE-2026-45076 is a low-severity vulnerability in Element Synapse, classified under Improper Input Validation. CVSS score: 2.7/10. Published 2026-05-28.

How severe is CVE-2026-45076?

Low severity. CVSS v3 base score is 2.7 out of 10.

Improper input validation in Element Synapse

CVE-2026-45076

Synapse is an open source Matrix homeserver implementation. Prior to 1.152.1, in federated rooms, malicious homeservers can craft room events in such a way that prevents Synapse from providing full history to paginating clients. Clients could therefore fail to display room history. This vulnerability is fixed in 1.152.1.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2026-05-28 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 2.7 (Low). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

EPSS: 0.004 (29.9th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 30th percentile — 29.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: +0.000

Affected products

Element Synapse
Element-Hq Synapse — versions < 1.152.1

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

github.com/element-hq/synapse/security/advisories/GHSA-6qf2-7x63-mm6v (Vendor Advisory)

Frequently asked questions

What is CVE-2026-45076?: CVE-2026-45076 is a low-severity vulnerability in Element Synapse, classified under Improper Input Validation. CVSS score: 2.7/10. Published 2026-05-28.
How severe is CVE-2026-45076?: Low severity. CVSS v3 base score is 2.7 out of 10.