Description
Matrix Synapse before 0.28.1 is prone to a denial of service flaw where malicious events injected with depth = 2^63 - 1 render rooms unusable, related to federation/federation_base.py and handlers/message.py, as exploited in the wild in April 2018.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 18.04 LTS | matrix-synapse | 0.24.0+dfsg-1ubuntu0.1~esm1 | USN-6076-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | matrix-synapse | < 0.28.1 | 0.28.1 | GHSA-vmcc-4p4x-x7wg |
Advisories 1
- USN-6076-1 matrix-synapse vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026