CVE-2026-86351
MISP User Homepage Validation Allows Authenticated Open Redirect via Protocol-Relative URL
- State
- Published
- Severity
- 5.1 Medium
- Published
- Sep 7, 2026
- Updated
- Sep 8, 2026
- Reserved
- Sep 7, 2026
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
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 5.1 Medium | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N | CIRCL |
Weaknesses
Affected Products
| Product | Versions |
|---|---|
MISPMISP |
|
References
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