Improper input validation in Matrix Synapse
CVE-2020-26890
Matrix Synapse before 1.20.0 erroneously permits non-standard NaN, Infinity, and -Infinity JSON values in fields of m.room.member events, allowing remote attackers to execute a denial of service attack against the federation and common Matrix clients. If such a malformed event is accepted into the room's state, the impact is long-lasting and is not fixed by an upgrade to a newer version, requiring the event to be manually redacted instead. Since events are replicated to servers of other room members, the impact is not constrained to the server of the event sender.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.030 (86.9th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 87th percentile — 86.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.030 · newest: 0.030 · change: 0.000
Affected products
- Matrix Synapse
- Fedoraproject Fedora — versions 32, 33
Weakness classification (CWE)
References
- github.com/matrix-org/synapse/security/advisories/GHSA-4mp3-385r-v63f (Patch, Third Party Advisory)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
Frequently asked questions
- What is CVE-2020-26890?
- CVE-2020-26890 is a high-severity vulnerability in Matrix Synapse, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2020-11-24.
- How severe is CVE-2020-26890?
- High severity. CVSS v3 base score is 7.5 out of 10.