CVE-2026-45078

medium

Published 2026-05-14 · Modified 2026-06-03

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CVSS v3

5.5

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS v4 NEW

6.8

CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

VIR risk

5.5

Description

Synapse is an open source Matrix homeserver implementation. Prior to 1.152.1, 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. This vulnerability is fixed in 1.152.1.

Predictions

Exploit likelihood

55%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here with source_tier=community-verified.

OS impact

Debian Fixed 2 releases

Version	Status	Fixed in
sid	Fixed	`1.152.1-1`
forky	Fixed	`1.152.1-1`

Package impact

Ecosystem	Package	Vulnerable	Fixed
PyPI	matrix-synapse	`<1.152.1`	`1.152.1`
PIP	matrix-synapse	`< 1.152.1`	`1.152.1`

Application impact

Vendor	Product	Versions	Fixed
element	synapse	`{"endExcluding":"1.152.1"}`	`1.152.1`

References

CWEs

CWE-770

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.