What is CVE-2021-46520?

CVE-2021-46520 is a high-severity vulnerability in Cesanta Mjs, classified under Out-of-bounds Write. CVSS score: 7.8/10. Published 2022-01-27.

How severe is CVE-2021-46520?

High severity. CVSS v3 base score is 7.8 out of 10.

Buffer overflow in Cesanta Mjs

CVE-2021-46520

Cesanta MJS v2.20.0 was discovered to contain a heap buffer overflow via mjs_jprintf at src/mjs_util.c.

Vulnerability class: Buffer Overflow

Published 2022-01-27 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.007 (52.4th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 52nd percentile — 52.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Cesanta Mjs — versions 2.20.0

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

github.com/cesanta/mjs/issues/193 (Exploit, Third Party Advisory, Issue Tracking)

Frequently asked questions

What is CVE-2021-46520?: CVE-2021-46520 is a high-severity vulnerability in Cesanta Mjs, classified under Out-of-bounds Write. CVSS score: 7.8/10. Published 2022-01-27.
How severe is CVE-2021-46520?: High severity. CVSS v3 base score is 7.8 out of 10.