toeverything AFFiNE up to 0.25.3 URL code injection

Summaryinfo

A vulnerability classified as critical has been found in toeverything AFFiNE up to 0.25.3. Affected by this issue is some unknown functionality of the component URL Handler. Performing a manipulation results in code injection. This vulnerability is cataloged as CVE-2026-21853. It is possible to initiate the attack remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in toeverything AFFiNE up to 0.25.3. It has been classified as critical. This affects some unknown processing of the component URL Handler. The manipulation with an unknown input leads to a code injection vulnerability. CWE is classifying the issue as CWE-94. The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-21853 since 01/05/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1059 according to MITRE ATT&CK.

Upgrading to version 0.25.4 eliminates this vulnerability. Applying the patch c9a4129a3e9376b688c18e1dcd6c87a775caac80 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-9252). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• toeverything

Name

• AFFiNE

Version

• 0.25.0
• 0.25.1
• 0.25.2
• 0.25.3

License

• open-source

Website

• Product: https://github.com/toeverything/AFFiNE/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Discussion