CVE-2026-86351 MISP User Homepage Validation Allows Authenticated Open Redirect via Protocol-Relative URL
Authenticated users can trigger open redirects via protocol-relative URLs in homepage settings, potentially facilitating phishing attacks.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-86351?
CVE-2026-86351 is a medium-severity vulnerability in Misp-Project Misp, published on 7 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Affected versions of MISP validate the user-configurable homepage by checking only whether the supplied path begins with /. That check is insufficient because protocol-relative URLs such as //attacker.example also begin with / but resolve to an external origin in browsers.
The vulnerable homepage value can be stored as a user setting and later used by the post-login routing logic. The commit explicitly identifies //attacker.example as a payload that passed validation and was emitted to the Location header after login.
The fix introduces a shared InternalRedirectValidator that rejects URLs containing a host, scheme, userinfo, unsafe leading // or /\, malformed URLs, and control characters. It also revalidates homepage settings on read so legacy or internally written unsafe values cannot bypass the new storage-time validation.
Version affected: ≤2.5.45
Which versions are affected by CVE-2026-86351?
It affects 1 product.
Products include Misp-Project Misp.
How do I fix CVE-2026-86351?
No fix has been published for CVE-2026-86351 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-86351 being exploited?
There is no known exploitation of CVE-2026-86351 in the wild and no public exploit code.
Other vulnerabilities in Misp-Project Misp
Sources
Also known as GHSA-7q84-h6g5-j34g.