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CVE-2020-26891

Published: 19 October 2020

AuthRestServlet in Matrix Synapse before 1.21.0 is vulnerable to XSS due to unsafe interpolation of the session GET parameter. This allows a remote attacker to execute an XSS attack on the domain Synapse is hosted on, by supplying the victim user with a malicious URL to the /_matrix/client/r0/auth/*/fallback/web or /_matrix/client/unstable/auth/*/fallback/web Synapse endpoints.

Priority

Medium

Cvss 3 Severity Score

6.1

Score breakdown

Status

Package Release Status
matrix-synapse
Launchpad, Ubuntu, Debian
kinetic Ignored
(end of life, was needs-triage)
hirsute Ignored
(end of life)
bionic Needs triage

focal Needs triage

groovy Ignored
(end of life)
trusty Does not exist

upstream
Released (1.21.1-1)
xenial Does not exist

jammy Needs triage

impish Ignored
(end of life)
lunar Not vulnerable
(1.64.0-3)
mantic Not vulnerable
(1.64.0-3)

Severity score breakdown

Parameter Value
Base score 6.1
Attack vector Network
Attack complexity Low
Privileges required None
User interaction Required
Scope Changed
Confidentiality Low
Integrity impact Low
Availability impact None
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N