Input validation error in Synapse - CVE-2021-21274
Published: March 1, 2021
Vulnerability identifier: #VU51007
CSH Severity: Low
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2021-21274
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to insufficient validation of user-supplied input when requesting the .well-known file. A remote attacker can trick a victim to connect a specially crafted homeserver and perform a denial of service (DoS) attack.
Affected software
Synapse
Fedora
matrix-synapse
Fedora
matrix-synapse
How to mitigate CVE-2021-21274
Install updates from vendor's website.
Synapse - update to 1.25.0
matrix-synapse - addressed in versions 1.38.0-2.fc34, 1.38.1-1.fc34
matrix-synapse - addressed in versions 1.38.0-2.fc34, 1.38.1-1.fc34