PT-2020-16532 · Matrix+1 · Matrix Synapse+1
Published
2020-09-23
·
Updated
2021-07-21
·
CVE-2020-26890
CVSS v4.0
8.7
High
| Vector | AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
Name of the Vulnerable Software and Affected Versions
Matrix Synapse versions prior to 1.20.0
Description
The issue allows remote attackers to execute a denial of service attack against the federation and common Matrix clients by sending non-standard NaN, Infinity, and -Infinity JSON values in fields of m.room.member events. If 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.
Recommendations
For Matrix Synapse versions prior to 1.20.0, apply patches #8106 and #8291 at a minimum to address the issue. Additionally, patches #7372 and #8124 include additional checks. If an invalid event is accepted by an earlier Synapse, it can become part of the room state and will not be fixed by upgrading Synapse. Redacting the invalid event should avoid clients receiving the invalid event. As a temporary workaround, consider manually redacting any invalid events that have been accepted into the room's state until the patches are applied.
Fix
DoS
RCE
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Weakness Enumeration
Related Identifiers
Affected Products
Alt Linux
Matrix Synapse