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

> Attackers can achieve remote code execution on victim machines by tricking them into visiting a malicious site or clicking a crafted link that triggers the AFFiNE custom URL handler.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 2 Mar 2026
- **Updated:** 2 Mar 2026
- **Also known as:** GHSA-67vm-2mcj-8965

## What is CVE-2026-21853?

CVE-2026-21853 is a high-severity code injection vulnerability in toeverything AFFiNE, published on 2 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2026-21853?

It affects 1 product.


Products: Affine Affine.

## How do I fix CVE-2026-21853?

No fix has been published for CVE-2026-21853 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-21853 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-21853 exists.

## Other vulnerabilities in toeverything AFFiNE

- [CVE-2026-25477](https://insights.sbomify.com/CVE-2026-25477/): AFFiNE: Open Redirect via Regex Bypass in redirect-proxy (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-21853 and fix it if it is affected.

What it is: CVE-2026-21853 is a high-severity code injection vulnerability in toeverything AFFiNE, published on 2 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-21853 exists.

Affected product: toeverything AFFiNE. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-21853/ (Markdown: https://insights.sbomify.com/CVE-2026-21853/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-21853
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-21853
- OSV: https://osv.dev/vulnerability/CVE-2026-21853

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-21853/
Summaries are generated and may contain mistakes; the official description above is the record.