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.
Published 2020-10-19 17:15:13
Updated 2020-10-26 21:30:56
Source MITRE
View at NVD,   CVE.org
Vulnerability category: Cross site scripting (XSS)

Products affected by CVE-2020-26891

Exploit prediction scoring system (EPSS) score for CVE-2020-26891

0.13%
Probability of exploitation activity in the next 30 days EPSS Score History
~ 49 %
Percentile, the proportion of vulnerabilities that are scored at or less

CVSS scores for CVE-2020-26891

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source First Seen
4.3
MEDIUM AV:N/AC:M/Au:N/C:N/I:P/A:N
8.6
2.9
NIST
6.1
MEDIUM CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
2.8
2.7
NIST

CWE ids for CVE-2020-26891

References for CVE-2020-26891

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