How severe is CVE-2022-39335?

CVE-2022-39335 has a CVSS score of 5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2022-39335?

CVE-2022-39335 affects the following packages: matrix-synapse (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2022-39335?

Update matrix-synapse to 1.69.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-39335 is resolved across your whole dependency graph.

How do I detect CVE-2022-39335 in my PyPI dependencies?

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.

How do I mitigate CVE-2022-39335 if there is no patch (or I can't update yet)?

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.

Is CVE-2022-39335 actively exploited in the wild?

No public exploit code has been indexed for CVE-2022-39335 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2022-39335?

CVE-2022-39335 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 51th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2022-39335?

CVE-2022-39335 is classified as Information Exposure (CWE-200), CWE-862 (CWE-862). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2022-39335 published, and has it been updated?

CVE-2022-39335 was published on May 26, 2023 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

MEDIUM severity

CVE-2022-39335 — matrix-synapse

MEDIUMFix: matrix-org/synapse#13823

CVE-2022-39335 is a medium-severity (CVSS 5) Information Exposure vulnerability in matrix-synapse. A fix is available for matrix-synapse — see the affected versions and patch details below.

Synapse does not apply enough checks to servers requesting auth events of events in a room

Also known asGHSA-45cj-f97f-ggwvPYSEC-2023-65

Published

May 26, 2023

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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 CVE-2022-39335.

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs51th percentile — riskier than 51% of all scored CVEsHighest risk

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

1 pkg affected

🐍matrix-synapse

Real-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

Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. The Matrix Federation API allows remote homeservers to request the authorisation events of events in a room. This is necessary so that a homeserver receiving some events can validate that those events are legitimate and permitted in their room. However, in versions of Synapse up to and including 1.68.0, a Synapse homeserver answering a query for authorisation events does not sufficiently check that the requesting server should be able to access them.

Authorisation events include power level events (the list of user IDs and their power levels at the time) and relevant membership events (including the display name of the sender of that event), as well as events like m.room.create, m.room.third_party_invite and m.room.join_rules. Non-authorisation events are unaffected, so it isn't possible to e.g. extract message contents this way.

This issue is only exploitable when a malicious actor knows the ID of a target room and the ID of an event from that room. In most cases, this makes exploitation infeasible. This issue is of negligible consequence for public rooms given that any server can easily join the room in order to be allowed to view authorisation events. Further, deployments in a closed federation where all homeservers are trustworthy are not affected.

Patches

The issue was patched in Synapse 1.69.0. Homeserver administrators are advised to upgrade.

Workarounds

Synapse can be configured with a list of servers that it is allowed to federate with federation_domain_whitelist. If this list is in use and all the servers on the list are trusted not to exploit this issue, then this issue is of no consequence.

This workaround is not practical for homeservers participating in open federation as interaction with any server not on the list would have to happen indirectly through servers that are, leading to inconsistent delays in message delivery.

References

Fixed in https://github.com/matrix-org/synapse/pull/13823.

For more information

If you have any questions or comments about this advisory, e-mail us at [email protected].

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`matrix-synapse`	all versions	1.69.0`pip install --upgrade 'matrix-synapse==1.69.0'`

Affected Products

1 product · 1 configurations

Application

synapsematrix

< 1.69.0

range

Detection & mitigation playbook

Open-source dependency

Detect
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 1.69.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-39335 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

### Impact Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. The Matrix Federation API allows remote homeservers to request the *authorisation events* of events in a room. This is necessary so that a homeserver receiving some events can validate that those events are legitimate and permitted in their room. However, in versions of Synapse up to and including 1.68.0, a Synapse homeserver answering a query for authorisation events does not sufficiently check that the requesting server should be able to access them. Authorisation events include power