What is CVE-2021-21426?

CVE-2021-21426 is a critical-severity vulnerability in Openmage Magento, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2021-04-21.

How severe is CVE-2021-21426?

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

Deserialization in Openmage Magento

CVE-2021-21426

Magento-lts is a long-term support alternative to Magento Community Edition (CE). In magento-lts versions 19.4.12 and prior and 20.0.8 and prior, there is a vulnerability caused by the unsecured deserialization of an object. A patch in versions 19.4.13 and 20.0.9 was back ported from Zend Framework 3. The vulnerability was assigned CVE-2021-3007 in Zend Framework.

Vulnerability class: Insecure Deserialization

Published 2021-04-21 · 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: 0.012 (67.8th percentile), scored 2026-10-19.

Low probability of exploitation in the next 30 days, but still tracked. 68th percentile — 67.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.012 · newest: 0.012 · change: 0.000

Affected products

Openmage Magento
Openmage Magento-Lts — versions <= 19.4.12, <= 20.0.8

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

References

github.com/OpenMage/magento-lts/security/advisories/GHSA-m496-x567-f98c (Third Party Advisory)

Frequently asked questions

What is CVE-2021-21426?: CVE-2021-21426 is a critical-severity vulnerability in Openmage Magento, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2021-04-21.
How severe is CVE-2021-21426?: Critical severity. CVSS v3 base score is 9.8 out of 10.