CVE-2020-26891
high
CVSS v3
—
CVSS v2
—
VIR risk
8.0
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.
Predictions
Exploit likelihood
30%
Patch ETA
—
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2020-26891
Vendor advisory: arch — https://security.archlinux.org/ASA-202011-4
OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| arch | fixed | 1.21.0-1 | |
| debian | forky | fixed | 1.21.1-1 |
| debian | sid | fixed | 1.21.1-1 |
Package impact
| Ecosystem | Package | Vulnerable | Fixed |
|---|---|---|---|
| PyPI | matrix-synapse | <1.21.0 | 1.21.0 |
References
- https://github.com/matrix-org/synapse/security/advisories/GHSA-3x8c-fmpc-5rmq
- https://nvd.nist.gov/vuln/detail/CVE-2020-26891
- https://github.com/matrix-org/synapse/pull/8444
- https://github.com/matrix-org/synapse
- https://github.com/matrix-org/synapse/releases
- https://github.com/matrix-org/synapse/releases/tag/v1.21.2
- https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2020-238.yaml
- https://matrix.org/blog/2020/10/15/synapse-1-21-2-released-and-security-advisory
- https://security.archlinux.org/ASA-202011-4
- https://security-tracker.debian.org/tracker/CVE-2020-26891
Verify integrity in audit chain (admin only). AS-IS.