CVE-2026-21853: AFFiNE: One-click Remote Code Execution through Custom URL Handling

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-03-02 · updated 2026-06-17
Weakness: CWE-94

Description

AFFiNE is an open-source, all-in-one workspace and an operating system. Prior to version 0.25.4, there is a one-click remote code execution vulnerability. This vulnerability can be exploited by embedding a specially crafted affine: URL on a website. An attacker can trigger the vulnerability in two common scenarios: 1/ A victim visits a malicious website controlled by the attacker and the website redirect to the URL automatically, or 2/ A victim clicks on a crafted link embedded on a legitimate website (e.g., in user-generated content). In both cases, the browser invokes AFFiNE custom URL handler, which launches the AFFiNE app and processes the crafted URL. This results in arbitrary code execution on the victim’s machine, without further interaction. This issue has been patched in version 0.25.4.

Affected products

toeverything AFFiNE: before 0.25.4 — fixed in 0.25.4

How to fix

Upgrade to a fixed version: toeverything AFFiNE 0.25.4. Check the vendor advisory for mitigations.

References

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