CVE-2021-21393 Denial of service (via resource exhaustion) due to improper input validation on groups/communities endpoints

2021-04-1221:35:14

CWE-20

GitHub_M

www.cve.org

5.3 Medium

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

HIGH

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

7 High

AI Score

Confidence

High

0.002 Low

EPSS

Percentile

57.3%

JSON

Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.28.0 Synapse is missing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. Note that the groups feature is not part of the Matrix specification and the chosen maximum lengths are arbitrary. Not all clients might abide by them. Refer to referenced GitHub security advisory for additional details including workarounds.

CNA Affected

[
  {
    "product": "synapse",
    "vendor": "matrix-org",
    "versions": [
      {
        "status": "affected",
        "version": "< 1.28.0"
      }
    ]
  }
]