CVE-2021-21394

Exploitation

Not assessed. CISA has not published an exploitation assessment for this record, and it is not in the KEV catalog. That is an absence of assessment, not a finding of no risk.

SSVC decision

Not assessed by CISA

EPSS probability

1.54% probability of exploitation activity in the next 30 days.

EPSS percentile

Ranks above 73.2% of scored records. A rank, not a probability.

NVD base score

6.5 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD analysis status

Modified. NVD last modified this record on 2026-06-17.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2021-04-12 20:45Z5 YR AGO

Last updated

2024-08-03 18:09Z2 YR AGO

Reserved

2020-12-22

Assigning CNA

GitHub_M

Record state

PUBLISHED

Severity

Medium (CVSS 5.3)

CNA CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Weaknesses

• CWE-20Improper Input ValidationClass

Data version

5.1

Document digest

7adb5fae618052fce5a2a6fa050aabd072d7c2257567b806853aa0ea1cf4cf51

• github.comhttps://github.com/matrix-org/synapse/security/advisories/GHSA-w9fg-xffh-p362x_refsource_CONFIRM
• pypi.orghttps://pypi.org/project/matrix-synapse/x_refsource_MISC
• github.comhttps://github.com/matrix-org/synapse/pull/9321x_refsource_MISC
• github.comhttps://github.com/matrix-org/synapse/pull/9393x_refsource_MISC
• lists.fedoraproject.orgFEDORA-2021-a627cfd31ehttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/vendor-advisoryx_refsource_FEDORA