CVE-2021-21333

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

1.35% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 71.1% of scored records. A rank, not a probability.

NVD base score

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

NVD CVSS vector

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

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

2021-03-26 20:00Z5 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 6.1)

CNA CVSS vector

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

Weaknesses

• CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')Class
• CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')Base

Data version

5.1

Document digest

74e101edcad98a977f68d67aa90219c568d765e8163a6597f6574a9658e2a845

• github.comhttps://github.com/matrix-org/synapse/releases/tag/v1.27.0x_refsource_MISC
• github.comhttps://github.com/matrix-org/synapse/pull/9200x_refsource_MISC
• github.comhttps://github.com/matrix-org/synapse/commit/e54746bdf7d5c831eabe4dcea76a7626f1de73dfx_refsource_MISC
• github.comhttps://github.com/matrix-org/synapse/security/advisories/GHSA-c5f8-35qr-q4fmx_refsource_CONFIRM
• lists.fedoraproject.orgFEDORA-2021-a627cfd31ehttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/vendor-advisoryx_refsource_FEDORA