Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-21853 is a high-severity Code Injection (CWE-94) vulnerability in Affine Affine. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Command and Scripting Interpreter (T1059); ranked at the 46th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-21853 is a remote code execution vulnerability affecting AFFiNE, an open-source all-in-one workspace and operating system, in versions prior to 0.25.4. The flaw stems from improper handling of specially crafted "affine:" URLs by AFFiNE's custom URL handler, classified under CWE-94 (Code Injection). It carries a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H), indicating high severity due to its potential for network-based exploitation with low complexity and no privileges required.
Attackers can exploit this vulnerability without authentication by embedding a malicious "affine:" URL on a website. In one scenario, a victim visits an attacker-controlled site that automatically redirects to the URL; in another, the victim clicks a crafted link in user-generated content on a legitimate site. Either action triggers the victim's browser to invoke AFFiNE's handler, launching the app and processing the URL, resulting in arbitrary code execution on the victim's machine with no further interaction needed.
The vulnerability has been patched in AFFiNE version 0.25.4. The official security advisory (GHSA-67vm-2mcj-8965) and related pull request (#13864) on the project's GitHub repository detail the fix, implemented via commit c9a4129a3e9376b688c18e1dcd6c87a775caac80, which addresses the unsafe URL processing logic. Security practitioners should urge users to update to 0.25.4 or later and advise caution with "affine:" links from untrusted sources.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-9252
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.3.1
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation finds code paths that accept and execute externally influenced strings.
Input validation directly stops untrusted data from being used to construct executable code without neutralization.
Least privilege limits the damage an injected code fragment can perform once executed.
Requiring documented secure development standards and tools enforces use of safe code-generation APIs and escaping.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
PR.PS-06's SDLC practices directly target injection flaws via secure coding and testing (mostly), yet as a single broad outcome it leaves many code-generation specifics unaddressed (partial).
PR.DS-10 protects runtime data confidentiality/integrity but has no bearing on neutralizing externally influenced input during code generation, so neither direction shows any preventive effect.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Banning unapproved code samples and unauthenticated web services, combined with secure-coding standards and SAST, prevents the dynamic generation or inclusion of attacker-supplied code.