The vulnerability CVE-2025-6021 exists in libxml2's xmlBuildQName function due to integer overflow in buffer size calculations, resulting in a stack-based buffer overflow. This can cause memory corruption or denial of service. The issue affects Red Hat Enterprise Linux versions 8 (>=8.0.0 <8.10.1) and 10 (>=10.0.0 <10.2.5). Red Hat has issued security advisories RHSA-2025:10630 and RHSA-2025:10698 providing patches that fix this vulnerability along with other related libxml2 issues. The CVSS v3.1 base score is 7.5 (high severity) with network attack vector, low attack complexity, no privileges or user interaction required, and an impact limited to availability (denial of service).

Successful exploitation of this vulnerability can cause a denial of service due to a stack-based buffer overflow triggered by integer overflow in libxml2's xmlBuildQName function. There is no confirmed impact on confidentiality or integrity. No known exploits are reported in the wild at this time.

Red Hat has released official security updates for libxml2 that address CVE-2025-6021. Users should apply the updates as described in Red Hat advisories RHSA-2025:10630 and RHSA-2025:10698. The advisories provide detailed instructions for updating affected Red Hat Enterprise Linux 8 and 10 systems. Applying these patches mitigates the vulnerability. No additional mitigation steps are indicated by the vendor.