How severe is CVE-2021-33439?

CVE-2021-33439 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-33439 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33439?

CVE-2021-33439 affects Cesanta Mjs. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-33439?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-33439 published?

CVE-2021-33439 was published on 2022-07-26 and last updated on 2026-06-17.

CVE-2021-33439

CVE-2021-33439 is a medium-severity vulnerability in Cesanta Mjs with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-190.

Key facts

Severity: Medium (CVSS 3.x base score 5.5)
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-190
Affected product: Cesanta Mjs
Published: 2022-07-26
Last modified: 2026-06-17

Description

An issue was discovered in mjs (mJS: Restricted JavaScript engine), ES6 (JavaScript version 6). There is Integer overflow in gc_compact_strings() in mjs.c.

Frequently asked questions

What is CVE-2021-33439?: An issue was discovered in mjs (mJS: Restricted JavaScript engine), ES6 (JavaScript version 6). There is Integer overflow in gc_compact_strings() in mjs.c.
How severe is CVE-2021-33439?: CVE-2021-33439 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-33439 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33439?: CVE-2021-33439 affects Cesanta Mjs. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-33439?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-33439 published?: CVE-2021-33439 was published on 2022-07-26 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:cesanta:mjs:*:*:*:*:*:*:*:*

More vulnerabilities in Cesanta Mjs

CVE-2023-50044 — Critical (CVSS 9.8): Cesanta MJS 2.20.0 has a getprop_builtin_foreign out-of-bounds read if a Built-in API name occurs in a substring of an…
CVE-2023-43338 — Critical (CVSS 9.8): Cesanta mjs v2.20.0 was discovered to contain a function pointer hijacking vulnerability via the function…
CVE-2021-46527 — High (CVSS 7.8): Cesanta MJS v2.20.0 was discovered to contain a heap buffer overflow via mjs_get_cstring at src/mjs_string.c.
CVE-2021-46526 — High (CVSS 7.8): Cesanta MJS v2.20.0 was discovered to contain a global buffer overflow via snquote at src/mjs_json.c.
CVE-2021-46525 — High (CVSS 7.8): Cesanta MJS v2.20.0 was discovered to contain a heap-use-after-free via mjs_apply at src/mjs_exec.c.
CVE-2021-46524 — High (CVSS 7.8): Cesanta MJS v2.20.0 was discovered to contain a heap buffer overflow via snquote at mjs/src/mjs_json.c.

All CVEs affecting Cesanta Mjs →

Other CWE-190 (Integer Overflow or Wraparound) vulnerabilities

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CVE-2025-64721 — Critical (CVSS 10.0): Sandboxie is a sandbox-based isolation software for 32-bit and 64-bit Windows NT-based operating systems. In versions…
CVE-2015-5108 — Critical (CVSS 10.0): Integer overflow in Adobe Reader and Acrobat 10.x before 10.1.15 and 11.x before 11.0.12, Acrobat and Acrobat Reader DC…
CVE-2015-5097 — Critical (CVSS 10.0): Integer overflow in Adobe Reader and Acrobat 10.x before 10.1.15 and 11.x before 11.0.12, Acrobat and Acrobat Reader DC…
CVE-2013-2555 — Critical (CVSS 10.0): Integer overflow in Adobe Flash Player before 10.3.183.75 and 11.x before 11.7.700.169 on Windows and Mac OS X, before…

Browse all CWE-190 (Integer Overflow or Wraparound) vulnerabilities →