CVE-2020-26890

HIGH
7.5
CVSS Score
Published: November 24, 2020 at 02:07 AM UTC
Updated: June 17, 2026 at 03:08 AM UTC
2 products affected across 2 vendorsFedoraSynapse

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Severity
HIGH7.5
Exploit prediction
EPSS 3%

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 1.20.0
Affected range stops below 1.20.0, so it looks safe — our inference, not a vendor statement

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-20

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