Description
Matrix Synapse before 0.33.3.1 allows remote attackers to spoof events and possibly have unspecified other impacts by leveraging improper transaction and event signature validation.
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 | >= 0.33.3, < 0.33.3.1 | 0.33.3.1 | GHSA-fmvh-rvq5-hhjx |
| PyPI | matrix-synapse | < 0.33.2.1 | 0.33.2.1 | GHSA-fmvh-rvq5-hhjx |
| PyPI | matrix-synapse | < 0.33.2.1 · >= 0.33.3, < 0.33.3.1 | 0.33.2.1, 0.33.3.1 | PYSEC-2026-845 |
Advisories 1
- USN-6076-1 matrix-synapse vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026