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TI-2026-17555 Aliases CVE-2026-21853

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

Priority HIGH 73CWE-94Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-94.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00713 53rd percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed AFFiNE (toeverything): 0.25.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
toeverythingAFFiNEbefore 0.25.40.25.4Patch availableCNA
  • AFFiNE Vendortoeverything Affected before 0.25.4 Fixed in 0.25.4 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:affine:affine:*:*:*:*:*:*:*:*before 0.25.4Vulnerableaffine
  • cpe:2.3:a:affine:affine:*:*:*:*:*:*:*:* Versions before 0.25.4 Vulnerable ·affine

Remediation

  • Fix · CNA AFFiNE (toeverything) Fixed in 0.25.4

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-21853
  2. 2026-10-28 EPSS moved to the 50th–90th percentile

References

  • TI-2026-06784 toeverything AFFiNE Public Markdown Preview Endpoint :docId allowDocPreview authorization CVSS 4.0MEDIUM 6.9
  • TI-2025-10952 toeverything AFFiNE Avatar Upload Image Endpoint cross site scripting CVSS 4.0MEDIUM 5.1

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences