GHSA-p9qp-c452-f9r7 CVE-2022-39374 PYSEC-2023-66
Synapse Denial of service due to incorrect application of event authorization rules during state resolution
- Severity
- 0.0 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 0.94%
- Chance of exploitation in the next 30 days. Higher than 60.99% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-400 Uncontrolled Resource Consumption
- Fix
1.68.0rc1- Upgrade matrix-synapse to this version or later
Description
Impact
If Synapse and a malicious homeserver are both joined to the same room, the malicious homeserver can trick Synapse into accepting previously rejected events into its view of the current state of that room. This can be exploited in a way that causes all further messages and state changes sent in that room from the vulnerable homeserver to be rejected.
Synapse homeservers are affected by this issue if and only if they are joined to rooms which members of untrusted homeservers are joined or invited to.
- Synapse homeservers in rooms available over public federation are affected.
- Synapse homeservers with federation disabled are not affected.
- Synapse homeservers in a closed federation containing only trusted servers are not affected.
- Synapse homeservers which are only joined to rooms with federation disabled[^1] are not affected.
Patches
Administrators of homeservers with federation enabled are advised to upgrade to 1.68.0 or higher.
Workarounds
- Federation can be disabled by setting
federation_domain_whitelistto an empty list ([]). from the vulnerable homeserver to be rejected. This issue has been patched in version 1.68.0
References
[^1]: See m.federate in the m.room.create definition.
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 | >= 1.62.0, < 1.68.0rc1 |
1.68.0rc1 |
| matrix-synapse | >= 1.62.0, < 1.68.0 |
1.68.0 |
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 → 1.68.0rc1
- pip
pip install --upgrade "matrix-synapse>=1.68.0rc1"- poetry
poetry add "matrix-synapse>=1.68.0rc1"- uv
uv add "matrix-synapse>=1.68.0rc1"
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- Low
- User interaction
- None
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- High
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
CVSS 3.1 6.5
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
CWE-400: Uncontrolled Resource Consumption
The product does not properly control the allocation and maintenance of a limited resource.
How to prevent it
- Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
- Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question. The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
- Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
- Implementation: Ensure that all failures in resource allocation place the system into a safe posture.
References
Advisories
Packages
Other links
- github.com/matrix-org/synapse/security/advisories/GHSA-p9qp-c452-f9r7
- github.com/matrix-org/synapse/pull/13723
- github.com/matrix-org/synapse/commit/b73cbb82157d9666e8d667733afebc0d09ed858c
- github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2023-66.…
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UJIJR…
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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