CVE-2021-28556

Magento versions 2.4.2 (and earlier), 2.4.1-p1 (and earlier) and 2.3.6-p1 (and earlier) are affected by a DOM-based Cross-Site Scripting vulnerability on mage-messages cookies. Successful exploitation could lead to arbitrary JavaScript execution by an unauthenticated attacker. User interaction is required for successful exploitation.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2021-28556 has a CVSS score of 6.9 (Medium). The vector is network-reachable, high privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.4.2-p1, 2.3.7); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2021-28556? CVE-2021-28556 is a medium-severity cross-site scripting (XSS) vulnerability in magento/community-edition (composer), affecting versions >= 2.4.0, < 2.4.2-p1. It is fixed in 2.4.2-p1, 2.3.7. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2021-28556? CVE-2021-28556 has a CVSS score of 6.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2021-28556?
   • magento/community-edition (composer) (versions >= 2.4.0, < 2.4.2-p1)
   • magento/project-community-edition (composer) (versions <= 2.0.2)
4. Is there a fix for CVE-2021-28556? Yes. CVE-2021-28556 is fixed in 2.4.2-p1, 2.3.7. Upgrade to this version or later.
5. Is CVE-2021-28556 exploitable, and should I be worried? Whether CVE-2021-28556 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-28556 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-28556?
   • Upgrade magento/community-edition to 2.4.2-p1 or later
   • Upgrade magento/community-edition to 2.3.7 or later

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