What is CVE-2021-25763?

CVE-2021-25763 is a medium-severity vulnerability in Jetbrains Ktor, classified under Use of a Broken or Risky Cryptographic Algorithm. CVSS score: 5.3/10. Published 2021-02-03.

How severe is CVE-2021-25763?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Jetbrains Ktor

CVE-2021-25763

In JetBrains Ktor before 1.4.2, weak cipher suites were enabled by default.

Vulnerability class: POODLE (CVE-2014-3566)

Published 2021-02-03 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.005 (44.4th percentile), scored 2026-10-20.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 44.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Jetbrains Ktor

Weakness classification (CWE)

CWE-327 — Use of a Broken or Risky Cryptographic Algorithm

References

blog.jetbrains.com (Product)
blog.jetbrains.com/blog/2021/02/03/jetbrains-security-bulletin-q4-2020/ (Vendor Advisory)

Frequently asked questions

What is CVE-2021-25763?: CVE-2021-25763 is a medium-severity vulnerability in Jetbrains Ktor, classified under Use of a Broken or Risky Cryptographic Algorithm. CVSS score: 5.3/10. Published 2021-02-03.
How severe is CVE-2021-25763?: Medium severity. CVSS v3 base score is 5.3 out of 10.