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Vulnerability record · CVE-2021-3672 · published 23 November 2021

CVE-2021-3672: C-ares project c-ares cross-site scripting vulnerability

C Ares Project · C Ares

A flaw was found in c-ares library, where a missing input validation check of host names returned by DNS (Domain Name Servers) can lead to output of wrong hostnames which might potentially lead to Domain Hijacking. The highest threat from this vulnerability is to confidentiality and integrity as well as system availability.

5.6 CVSS 3.1 Medium EPSS 2.8% · top 14.0% CWE-79 · Cross-site scripting
5.6CVSS 3.1 base score, v2 6.8
2.8%EPSS exploitation probability, 30 days
NoNot in CISA KEV
17Affected product versions listed by NVD
10References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

A flaw was found in c-ares library, where a missing input validation check of host names returned by DNS (Domain Name Servers) can lead to output of wrong hostnames which might potentially lead to Domain Hijacking. The highest threat from this vulnerability is to confidentiality and integrity as well as system availability.

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

Affected products

17 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugzilla.redhat.com/show_bug.cgi?id=1988342 Issue TrackingThird Party Advisory
https://c-ares.haxx.se/adv_20210810.html ExploitPatchVendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf PatchThird Party Advisory
https://security.gentoo.org/glsa/202401-02
https://www.oracle.com/security-alerts/cpujul2022.html Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1988342 Issue TrackingThird Party Advisory
https://c-ares.haxx.se/adv_20210810.html ExploitPatchVendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf PatchThird Party Advisory
https://security.gentoo.org/glsa/202401-02
https://www.oracle.com/security-alerts/cpujul2022.html Third Party Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-3672), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.