Improper input validation in Matrix Synapse
CVE-2021-21393
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.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.016 (74.8th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 75th percentile — 74.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.016 · newest: 0.016 · change: 0.000
Affected products
- Matrix Synapse
- Matrix-Org Synapse — versions < 1.28.0
- Fedoraproject Fedora — versions 34
Weakness classification (CWE)
References
- pypi.org/project/matrix-synapse/ (Product, Third Party Advisory)
- github.com/matrix-org/synapse/pull/9321 (Patch, Third Party Advisory)
- github.com/matrix-org/synapse/pull/9393 (Patch, Third Party Advisory)
- github.com/matrix-org/synapse/security/advisories/GHSA-jrh7-mhhx-6h88 (Patch, Third Party Advisory)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
Frequently asked questions
- What is CVE-2021-21393?
- CVE-2021-21393 is a medium-severity vulnerability in Matrix Synapse, classified under Improper Input Validation. CVSS score: 5.3/10. Published 2021-04-12.
- How severe is CVE-2021-21393?
- Medium severity. CVSS v3 base score is 5.3 out of 10.