CVE-2020-26891

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.
Cross-site Scripting
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTNIST
6.1 MEDIUM
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
mitreCNA
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CVEADP
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Base Score
CVSS 3.x
EPSS Score
Percentile: 68%
VendorProductVersion
matrixsynapse
𝑥
< 1.21.0
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
matrix-synapse
sid
1.116.0-3
fixed
trixie
1.116.0-3
fixed
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
matrix-synapse
noble
not-affected
mantic
not-affected
lunar
not-affected
kinetic
ignored
jammy
needs-triage
impish
ignored
hirsute
ignored
groovy
ignored
focal
needs-triage
bionic
needs-triage
xenial
dne
trusty
dne
Common Weakness Enumeration
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
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