CVE-2020-26891

medium

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.

References

https://github.com/matrix-org/synapse/pull/8444

https://github.com/matrix-org/synapse/releases/tag/v1.21.2

https://github.com/matrix-org/synapse/security/advisories/GHSA-3x8c-fmpc-5rmq

https://matrix.org/blog/2020/10/15/synapse-1-21-2-released-and-security-advisory

Details

Source: MITRE

Published: 2020-10-19

Updated: 2020-10-26

Type: CWE-79

Risk Information

CVSS v2

Base Score: 4.3

Vector: AV:N/AC:M/Au:N/C:N/I:P/A:N

Impact Score: 2.9

Exploitability Score: 8.6

Severity: MEDIUM

CVSS v3

Base Score: 6.1

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Impact Score: 2.7

Exploitability Score: 2.8

Severity: MEDIUM