Is CVE-2026-53421 in the CISA KEV catalog?

No. CVE-2026-53421 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-53421?

CVE-2026-53421 has a CVSS v3 base score of 9.8 (CRITICAL).

How do I fix or mitigate CVE-2026-53421?

No published fix for CVE-2026-53421 has been found yet. Check the linked vendor advisories for guidance as it becomes available.

CVE & CISA-KEV Catalog

CVE-2026-53421

CRITICAL

9.8

CVSS v3

NVD

Description

Improper Isolation or Compartmentalization vulnerability in Apache Syncope. An administrator with adequate entitlements can achieve remote code execution through the connector subsystem by relying on scripted connectors' (REST and SQL) capability to run Groovy scripts. This issue affects Apache Syncope: from 3.0.0-M0 through 3.0.16, from 4.0.0-M0 Through 4.0.6, from 4.1.0-M0 through 4.1.1. Users are recommended to upgrade to version 4.0.7 / 4.1.2, which fix this issue by hardening the Groovy security sandbox.

CWE-653

How to fix

No published remediation has been found for this vulnerability's affected products yet.

Mitigation guidance may be in the linked vendor advisories in the References section below.

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CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploit Intelligence

EPSS data unavailable for this CVE.

References

Other references2

Related Vulnerabilities

Other CWE-653 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-1974	Critical	9.8	99%	-	-
CVE-2025-57738	High	7.2	23%	-	Fix
CVE-2025-21590	Medium	4.4	1.7%	KEV	-
CVE-2026-24781	Critical	9.8	1.2%	-	Fix
CVE-2024-0135	High	7.6	1.1%	-	Fix
CVE-2026-43997	Critical	10.0	1.0%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-21.