What is CVE-2023-43338?

CVE-2023-43338 is a critical-severity vulnerability in Cesanta Mjs, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2023-09-23.

How severe is CVE-2023-43338?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Cesanta Mjs

CVE-2023-43338

Cesanta mjs v2.20.0 was discovered to contain a function pointer hijacking vulnerability via the function mjs_get_ptr(). This vulnerability allows attackers to execute arbitrary code via a crafted input.

Vulnerability class: Buffer Overflow

Published 2023-09-23 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.010 (60.9th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 61st percentile — 60.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.010 · change: +0.001

Affected products

Cesanta Mjs — versions 2.20.0

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

github.com/cesanta/mjs/issues/250 (Exploit, Issue Tracking, Vendor Advisory)

Frequently asked questions

What is CVE-2023-43338?: CVE-2023-43338 is a critical-severity vulnerability in Cesanta Mjs, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2023-09-23.
How severe is CVE-2023-43338?: Critical severity. CVSS v3 base score is 9.8 out of 10.