Resource exhaustion in synapse (Alpine package)

1) Resource exhaustion

EUVDB-ID: #VU49037

Risk: Medium

CVSSv4.0: 4.9 [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/E:U/U:Green]

CVE-ID: CVE-2020-26257

CWE-ID: CWE-400 - Resource exhaustion

Exploit availability: No

Description

The vulnerability allows a remote authenticated user to perform a denial of service (DoS) attack.

Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference "homeserver" implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).

Mitigation

Install update from vendor's website.

Vulnerable software versions

wireshark (Alpine package): 3.4.0-r0

synapse (Alpine package): 1.23.0-r0

CPE2.3

• cpe:2.3:o:alpine:wireshark_alpine_package:3.4.0-r0:*:*:*:*:alpine_linux:*:3.12
• cpe:2.3:o:alpine:synapse_alpine_package:1.23.0-r0:*:*:*:*:alpine_linux:*:3.12

External links

https://git.alpinelinux.org/aports/commit/?id=14a2aac38244afd14d093fdd32234385a1f94d43

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.