How severe is CVE-2026-71253?

CVE-2026-71253 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-71253 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-71253?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2026-71253 published?

CVE-2026-71253 was published on 2026-10-19 and last updated on 2026-10-20.

CVE-2026-71253

CVE-2026-71253 is a critical-severity vulnerability with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-470.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 1% (51st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-470
Published: 2026-10-19
Last modified: 2026-10-20

Description

Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') vulnerability in Apache Johnzon. ClassConverter loads & static-initializes an attacker-named class from untrusted JSON. This issue affects Apache Johnzon: from 1.0.0 before 2.2.0. Users are recommended to upgrade to version 1.3.1 (javax namespace) or 2.2.0 (jakarta specification namespace), which fixes the issue.

Frequently asked questions

What is CVE-2026-71253?: Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') vulnerability in Apache Johnzon. ClassConverter loads & static-initializes an attacker-named class from untrusted JSON. This issue affects Apache Johnzon: from 1.0.0 before 2.2.0. Users are recommended to upgrade to version 1.3.1 (javax namespace) or 2.2.0 (jakarta specification namespace), which fixes the issue.
How severe is CVE-2026-71253?: CVE-2026-71253 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-71253 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-71253?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2026-71253 published?: CVE-2026-71253 was published on 2026-10-19 and last updated on 2026-10-20.

References

Other CWE-470 (Unsafe Reflection) vulnerabilities

CVE-2026-78030 — Critical (CVSS 9.8): DBI versions before 1.653 for Perl load arbitrary modules via unvalidated dbm_type and dbm_mldbm attributes in…
CVE-2026-93762 — Critical (CVSS 9.8): Mongoid contains an unsafe reflection weakness in the query path used for embedded documents. An application that…
CVE-2026-41871 — Critical (CVSS 9.8): Missing Authorization, Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')…
CVE-2026-40008 — Critical (CVSS 9.8): Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') vulnerability in Apache IoTDB. The…
CVE-2026-42027 — Critical (CVSS 9.8): Arbitrary Class Instantiation via Model Manifest in Apache OpenNLP ExtensionLoader Versions Affected: before…
CVE-2025-34393 — Critical (CVSS 9.8): Barracuda Service Center, as implemented in the RMM solution, in versions prior to 2025.1.1, does not correctly verify…

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