CVE-2026-21853

HIGHNVD 8.88.8—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.8 under NVD CVSS v3. EPSS exploit probability: 0.6%, top 55% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 8.8Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
8.8
EG Score
8.8(medium)
EG Risk
56(Track*)
EG Risk 56/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity88% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
1%
EPSS %ILE
46%
KEV
Not listed

Published

March 2, 2026

Last Modified

June 17, 2026

Advisory Details (3)

Auto-updated Jun 7, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_pr, github.
github Patch Available🟡 PoC Available

One-click Remote Code Execution through Custom URL Handling in AFFiNE v0.25.1 · Advisory · toeverything/AFFiNE · GitHub

https://github.com/toeverything/AFFiNE/security/advisories/GHSA-67vm-2mcj-8965
github_pr

fix: a security issue related to open external

Fix merged in toeverything/AFFiNE PR #13864 on 2025-11-06 — awaiting tagged release

https://github.com/toeverything/AFFiNE/pull/13864
github_commit

commit c9a4129a3e93 (toeverything/AFFiNE)

Fix landed in toeverything/AFFiNE commit c9a4129a3e93 — awaiting tagged release

https://github.com/toeverything/AFFiNE/commit/c9a4129a3e9376b688c18e1dcd6c87a775caac80

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 45× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 122 total refreshes for this CVE.

  1. 2026-08-01 04:15 UTCEPSS rescore
  2. 2026-07-30 01:30 UTCEPSS rescore
  3. 2026-07-27 14:13 UTCEPSS rescore
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  11. 2026-07-23 03:06 UTCEG score recompute
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  1. 2026-07-15 16:57 UTCEPSS rescore
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  23. 2026-06-30 23:22 UTCEPSS rescore
  24. 2026-06-29 14:06 UTCEPSS rescore
  25. 2026-06-29 09:32 UTCOSV refresh
  26. 2026-06-28 14:07 UTCEPSS rescore
  27. 2026-06-28 04:56 UTCEPSS rescore
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  29. 2026-06-27 03:08 UTCEPSS rescore
  30. 2026-06-25 13:49 UTCEPSS rescore
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  44. 2026-06-14 23:18 UTCEPSS rescore
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  69. 2026-06-01 11:43 UTCOSV refresh
  70. 2026-05-31 22:30 UTCEPSS rescore
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  72. 2026-05-31 00:16 UTCEPSS rescore
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  74. 2026-05-31 00:16 UTCEPSS rescore
  75. 2026-05-29 13:44 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2026-21853?
CVE-2026-21853 is a high vulnerability published on March 2, 2026. 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…
When was CVE-2026-21853 disclosed?
CVE-2026-21853 was first published in the National Vulnerability Database on March 2, 2026, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-21853 actively exploited?
CVE-2026-21853 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 54.4% of all scored CVEs.
What is the CVSS score of CVE-2026-21853?
CVE-2026-21853 has a CVSS v3 base score of 8.8 (NVD).
How do I remediate CVE-2026-21853?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-21853, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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