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CVE-2020-26891

nvd nist
Published: Oct 19, 2020Modified: Jun 17, 2026

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6.1
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Exploitability: 2.8 / Impact: 2.7
Source: NVD

Description

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.

Affected (1)

Products: Matrix: Synapse
Matrix
1 product
Synapse
Configuration A
1 vulnerable
Vulnerable SoftwareAffected Versions
Synapse
Before 1.21.0

Related CWEs

CWE-79
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

References (8)

Source: cve@mitre.org
Issue TrackingPatchThird Party Advisory
Source: cve@mitre.org
Release NotesThird Party Advisory
Source: cve@mitre.org
PatchThird Party Advisory
Source: cve@mitre.org
Release NotesVendor Advisory
Source: af854a3a-2127-422b-91ae-364da2661108
Issue TrackingPatchThird Party Advisory
Source: af854a3a-2127-422b-91ae-364da2661108
Release NotesThird Party Advisory
Source: af854a3a-2127-422b-91ae-364da2661108
PatchThird Party Advisory
Source: af854a3a-2127-422b-91ae-364da2661108
Release NotesVendor Advisory

Timeline

No history available yet.