CVE-2025-46340 Details
Description
Misskey is an open source, federated social media platform. Starting in version 12.0.0 and prior to version 2025.4.1, due to an oversight in the validation performed in `UrlPreviewService` and `MkUrlPreview`, it is possible for an attacker to inject arbitrary CSS into the `MkUrlPreview` component. `UrlPreviewService.wrap` falls back to returning the original URL if it's using a protocol that is likely to not be understood by Misskey, IE something other than `http` or `https`. This both can de-anonymize users and_allow further attacks in the client. Additionally, `MkUrlPreview` doesn't escape CSS when applying a `background-image` property, allowing an attacker to craft a URL that applies arbitrary styles to the preview element. Theoretically, an attacker can craft a CSS injection payload to create a fake error message that can deceive the user into giving away their credentials or similar sensitive information. Version 2025.4.1 contains a patch for the issue.
A CSS injection vulnerability has been identified in the Misskey social media platform, affecting versions 12.0.0 through 2025.4.1. The issue arises from inadequate validation in the 'UrlPreviewService' and 'MkUrlPreview' components, allowing attackers to inject arbitrary CSS. The 'UrlPreviewService.wrap' method improperly handles URLs with unrecognized protocols, which can de-anonymize users and facilitate further client-side attacks. Moreover, the 'MkUrlPreview' component fails to properly escape CSS in 'background-image' properties, enabling the application of malicious styles to preview elements. Exploitation could involve creating a fake error message to trick users into revealing sensitive information, such as credentials.
Users can update to Misskey version 2025.4.1 or later, where this vulnerability has been patched.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 5, 2025References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-116 | Improper Encoding or Escaping of Output | [email protected] |
| CWE-20 | Improper Input Validation | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| misskey misskey | >= 12.0.0, < 2025.4.1 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Sep 3, 2025 | Initial Analysis | [email protected] |
| May 5, 2025 | New CVE Received | [email protected] |