🛡️ CVE-2026-45076 — matrix-synapse

🟢 CVSS 2.7 — Low ✅ No Known Exploit CWE-20 NVD
2.7
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Synapse pagination Denial of Service

Impact

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.

Patches

Update to Synapse 1.152.1 or later.

Workarounds

There are no known workarounds for this issue.

Identifiers

  • ELEMENTSEC-2025-1636

For more information

If you have any questions or comments about this advisory, please email us at [security at element.io](mailto:security@element.io).

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs administrative privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability low.

Weakness class

CVE-2026-45076 is classified as CWE-20: Improper Input Validation. The application accepts input without checking that it has the expected form, so malformed values reach code that assumes they are well formed.

Affected software

CVE-2026-45076 is recorded against 2 packages.

  • matrix-synapse (fixed in 1.152.1)
  • synapse (fixed in 1.152.1)

Timeline and source

Published on 28 May 2026 and last revised on 9 June 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Advisory)

CVE-2026-45076 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Low
CVSS Score 2.7
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L
CWE CWE-20
Public Exploit ✅ No
Source NVD
Published 2026-05-28
Updated 2026-08-20
Modified 2026-06-09
Fix URL N/A

Affected Packages

Software From version Fixed in
matrix-synapse — 1.152.1
synapse — 1.152.1

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