AUGUST 4, 2026
Live Feed
Back to database
Case File

CVE-2020-26891

MEDIUM · CVSS 6.1 EPSS 1.93% Public Exploit

Source: NVD + CISA KEV + EPSS (historical backfill) · Published 2020-10-19 · Last synced 2026-08-04

CyberRota Analysis

This is a medium severity vulnerability with a CVSS score of 6.1. Public exploit code or proof-of-concept references have been detected in its references. It may be remotely exploitable.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2020-26891
Severity
MEDIUM
CVSS
6.1
EPSS
1.93%

Original 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.

Related CVEs

Other vulnerabilities affecting the same vendor(s)