GHSA-45cj-f97f-ggwv CVE-2022-39335 PYSEC-2023-65
Synapse does not apply enough checks to servers requesting auth events of events in a room
- Severity
- 0.0 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 0.64%
- Chance of exploitation in the next 30 days. Higher than 50.44% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
- CWE-862 Missing Authorization
- Fix
1.69.0- Upgrade matrix-synapse to this version or later
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 security@matrix.org.
Affected versions
PyPI
| Package | Vulnerable | Fixed in |
|---|---|---|
| matrix-synapse | < 1.69.0 |
1.69.0 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
matrix-synapse PyPI → 1.69.0
- pip
pip install --upgrade "matrix-synapse>=1.69.0"- poetry
poetry add "matrix-synapse>=1.69.0"- uv
uv add "matrix-synapse>=1.69.0"
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- Attack vector
- Network
- Attack complexity
- High
- Attack requirements
- None
- Privileges required
- Low
- User interaction
- None
- Confidentiality (vulnerable system)
- High
- Integrity (vulnerable system)
- High
- Availability (vulnerable system)
- High
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
CVSS 3.1 5.0
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
Weakness
CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
How to prevent it
- Architecture and Design: Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
CWE-862: Missing Authorization
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
How to prevent it
- Architecture and Design: Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries. Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
- Architecture and Design: Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor [REF-7].
- Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
- Architecture and Design: For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page. One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.
- System Configuration, Installation: Use the access control capabilities of your operating system and server environment and define your access control lists accordingly. Use a "default deny" policy when defining these ACLs.
References
Advisories
Packages
Other links
- github.com/matrix-org/synapse/security/advisories/GHSA-45cj-f97f-ggwv
- github.com/matrix-org/synapse/issues/13288
- github.com/matrix-org/synapse/pull/13823
- github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2023-65.…
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/T2MBN…
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-6qf2-7x63-mm6v Synapse pagination Denial of Service | Low | Also affects matrix-synapse |
| GHSA-8q93-326v-3m7g Synapse CPU starvation (Denial of Service) | Medium | Also affects matrix-synapse |
| GHSA-fh66-fcv5-jjfr Synapse's invalid device keys degrade federation functionality | Medium | Also affects matrix-synapse |
| GHSA-v56r-hwv5-mxg6 Synapse vulnerable to federation denial of service via malformed events | High | Also affects matrix-synapse |
| GHSA-56w4-5538-8v8h Synapse Matrix has a partial room state leak via Sliding Sync | Medium | Also affects matrix-synapse |
| GHSA-vp6v-whfm-rv3g Synapse can be forced to thumbnail unexpected file formats, invoking external, potentially untrustworthy decoders | Critical | Also affects matrix-synapse |
| GHSA-f3r3-h2mq-hx2h Synapse allows a a malformed invite to break the invitee's `/sync` | Medium | Also affects matrix-synapse |
| GHSA-rfq8-j7rh-8hf2 Synapse allows unsupported content types to lead to memory exhaustion | High | Also affects matrix-synapse |
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