How severe is CVE-2021-43853?

CVE-2021-43853 has a CVSS 3.x base score of 8.7, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2021-43853 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43853?

CVE-2021-43853 affects Ajax.net Professional Project Ajax.net Professional. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-43853?

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

When was CVE-2021-43853 published?

CVE-2021-43853 was published on 2021-12-22 and last updated on 2026-06-17.

CVE-2021-43853

CVE-2021-43853 is a high-severity vulnerability in Ajax.net Professional Project Ajax.net Professional with a CVSS 3.x base score of 8.7. 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-502.

Key facts

Severity: High (CVSS 3.x base score 8.7)
CVSS v2: 3.5
EPSS exploit prediction: 1% (53rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-502
Affected product: Ajax.net Professional Project Ajax.net Professional
Published: 2021-12-22
Last modified: 2026-06-17

Description

Ajax.NET Professional (AjaxPro) is an AJAX framework available for Microsoft ASP.NET. Affected versions of this package are vulnerable to JavaScript object injection which may result in cross site scripting when leveraged by a malicious user. The affected core relates to JavaScript object creation when parsing json input. Releases before version 21.12.22.1 are affected. A workaround exists that replaces one of the core JavaScript files embedded in the library. See the GHSA-5q7q-qqw2-hjq7 for workaround details.

Frequently asked questions

What is CVE-2021-43853?: Ajax.NET Professional (AjaxPro) is an AJAX framework available for Microsoft ASP.NET. Affected versions of this package are vulnerable to JavaScript object injection which may result in cross site scripting when leveraged by a malicious user. The affected core relates to JavaScript object creation when parsing json input. Releases before version 21.12.22.1 are affected. A workaround exists that replaces one of the core JavaScript files embedded in the library. See the GHSA-5q7q-qqw2-hjq7 for workaround details.
How severe is CVE-2021-43853?: CVE-2021-43853 has a CVSS 3.x base score of 8.7, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-43853 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43853?: CVE-2021-43853 affects Ajax.net Professional Project Ajax.net Professional. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43853?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-43853 published?: CVE-2021-43853 was published on 2021-12-22 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:ajax.net_professional_project:ajax.net_professional:*:*:*:*:*:*:*:*

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