Login Request a demo
Medium severity · published Oct 19, 2020
CVE-2020-26891
AuthRestServlet in Matrix Synapse before 1.21.0 is vulnerable to XSS due to unsafe interpolation of the session GET parameter
6.1
CVSS
1.9%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)1.9% · higher than 80% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SY
Synapse · Matrix
before 1.21.0 · source: NVD
Affected product
SY
Synapse
Matrix
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-26891
CVE.org
https://www.cve.org/CVERecord?id=CVE-2020-26891
Issue Tracking
https://github.com/matrix-org/synapse/pull/8444
Release Notes
https://github.com/matrix-org/synapse/releases/tag/v1.21.2
Patch
https://github.com/matrix-org/synapse/security/advisories/GHSA-3x8c-fmpc-5rmq
Release Notes
https://matrix.org/blog/2020/10/15/synapse-1-21-2-released-and-security-advisory
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