Is CVE-2021-43853 in the CISA KEV catalog?

No. CVE-2021-43853 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-43853?

CVE-2021-43853 has a CVSS v3 base score of 8.7 (HIGH).

What is the EPSS score for CVE-2021-43853?

CVE-2021-43853 has an EPSS score of 0.82% (53th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-43853?

Upgrade ajax.net professional to 21.12.22.1 or later.

CVE & CISA-KEV Catalog

CVE-2021-43853

HIGH

8.7

CVSS v3

NVD

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.

CWE-79Cross-Site Scripting (XSS)CWE-502Deserialization of Untrusted Data

How to fix

Remediation Available

ajax.net professionalNVD

Affected:< 21.12.22.1Fixed in:21.12.22.1CVE-2021-43853derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow

User InteractionRequired

ScopeChanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

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

Exploit Intelligence

0.82%probability of exploitation in 30 days

53rdpercentile

Moderate risk: more likely to be exploited than 53% of all known CVEs.

References

Patch1

github.com

Mitigation1

github.com

Third-Party Advisory1

github.com

Related Vulnerabilities

Other CWE-79 (Cross-Site Scripting (XSS)) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2020-11022	Medium	6.9	99%	-	Fix
CVE-2019-3929	Critical	9.8	99%	KEV	Fix
CVE-2020-9496	Medium	6.1	99%	-	-
CVE-2023-28341	Medium	6.1	99%	-	Fix
CVE-2018-12998	Medium	6.1	98%	-	-
CVE-2025-4123	High	7.6	98%	-	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 2024-11-21.