Summary
Workarounds
There are no known workarounds.
Background
When you are anonymous and land on a page that requires a login, Plone sends you to the login form. After successful login, Plone redirects you back to the page you came from. Various other forms and pages have a similar system.
This could get abused by an attacker to trick Plone into redirecting to a different website. Plone checks the page that would be redirected to. It is only accepted if it is within the Plone site domain or part of a different trusted domain.
The main check for this is in the Products.isurlinportal package. A lot of potentially malicious urls are already safely rejected, but here a loop hole was found.
This was discovered during a penetration test by the CERT-EU Team.
Impact
A url /login?came_from=////evil.example may redirect to an external website after login.
Standard Plone is not affected, but if you have customised the login, for example with add-ons, you might be affected. You can try the url to check if you are affected or not.
Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites. Typical impact: phishing and credential harvesting via a trusted domain.
CVE-2026-28413 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. 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 (4.0.0, 3.1.0, 2.1.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
The problem has been patched in Products.isurlinportal.
- Plone 6.2: upgrade to
Products.isurlinportal4.0.0. - Plone 6.1: upgrade to
Products.isurlinportal3.1.0. - Plone 6.0: upgrade to
Products.isurlinportal2.1.0. - Older Plone versions don't have security support anymore.
Frequently Asked Questions
- What is CVE-2026-28413? CVE-2026-28413 is a medium-severity open redirect vulnerability in Products.isurlinportal (pip), affecting versions = 4.0.0a1. It is fixed in 4.0.0, 3.1.0, 2.1.0. Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites.
- How severe is CVE-2026-28413? CVE-2026-28413 has a CVSS score of 5.3 (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.
- Which packages are affected by CVE-2026-28413?
Products.isurlinportal(pip) (versions = 4.0.0a1)products-isurlinportal(pip) (versions >= 0, < 2.1.0)
- Is there a fix for CVE-2026-28413? Yes. CVE-2026-28413 is fixed in 4.0.0, 3.1.0, 2.1.0. Upgrade to this version or later.
- Is CVE-2026-28413 exploitable, and should I be worried? Whether CVE-2026-28413 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
- What actually determines whether CVE-2026-28413 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.
- How do I fix CVE-2026-28413?
- Upgrade
Products.isurlinportalto 4.0.0 or later - Upgrade
Products.isurlinportalto 3.1.0 or later - Upgrade
Products.isurlinportalto 2.1.0 or later - Upgrade
products-isurlinportalto 2.1.0 or later - Upgrade
products-isurlinportalto 3.1.0 or later
- Upgrade