Synapse has improper checks for deactivated users during loginGHSA-26c5-ppr8-f33p
MEDIUMFix: matrix-org/synapse#15624GHSA-26c5-ppr8-f33p is a medium-severity (CVSS 5.4) Improper Authentication vulnerability in matrix-synapse. A fix is available for matrix-synapse — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-26c5-ppr8-f33p.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
matrix-synapseReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
It may be possible for a deactivated user to login when using uncommon configurations.
This only applies if any of the following are true:
- JSON Web Tokens are enabled for login via the
jwt_config.enabledconfiguration setting - The local password database is enabled via the
password_config.enabledandpassword_config.localdb_enabledconfiguration settings and a user's password is updated via an admin API after a user is deactivated.
Note that the local password database is enabled by default, but it is uncommon to set a user's password after they've been deactivated.
Installations that are configured to only allow login via Single Sign-On (SSO) via CAS, SAML or OpenID Connect (OIDC); or via an external password provider (e.g. LDAP) are not affected.
Patches
- If using JSON Web Token logins: #15624
- For other users: #15634
Workarounds
If not using JSON Web Tokens, ensure that deactivated users do not have a password set. This list of users can be queried from PostgreSQL:
SELECT name FROM users WHERE password_hash IS NOT NULL AND deactivated = 1;
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | matrix-synapse | all versions | 1.85.0pip install --upgrade 'matrix-synapse==1.85.0' |
Affected Products
synapsematrixDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for matrix-synapse, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update matrix-synapse to 1.85.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-26c5-ppr8-f33p is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is GHSA-26c5-ppr8-f33p in your dependencies?
Find it across PyPI, including transitive dependencies.