High [CVE-2026-86140] Arbitrary code execution via stack-based buffer overflow in xmlSnprintfElements
This high-severity Red Hat Linux advisory covers CVE-2026-86140 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9.
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Summary
In libxml2 before 2.15.4, xmlSnprintfElements in valid.c has a strcat stack-based buffer overflow. A flaw was found in libxml2.
A local attacker could exploit a stack-based buffer overflow in the `xmlSnprintfElements` function to achieve arbitrary code execution. This vulnerability in a fundamental system library could lead to significant system compromise if successfully exploited.
Red Hat severity: Important — CVSS 7.4 (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-120.
Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Cert Manager support for Red Hat OpenShift release 1.20; Red Hat Cost Management On-Premise 1; Red Hat Hardened Images; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat OpenShift Container Platform 4.
Will not fix / out of support: Red Hat Enterprise Linux 6. Red Hat fixing advisory: RHSA-2026:71586, RHSA-2026:71641, RHSA-2026:71585, RHSA-2026:72470, RHSA-2026:72475, RHSA-2026:72476, RHSA-2026:79357, RHSA-2026:64463.
Affected products named by the advisory: Red Hat package: libxml2.
- < 2.15.4
Official advisory · high-confidence parse· fetched 22 days ago·verify at source
- libxml2-0:2.12.5-10.el10_2.4
- libxml2-0:2.9.7-21.el8_10.9
- libxml2-0:2.9.13-14.el9_8.5
- cert-manager/jetstack-cert-manager-rhel9:1790589912
- cert-manager/cert-manager-istio-csr-rhel9:1790589914
- cert-manager/cert-manager-operator-rhel9:1790589855
- costmanagement/costmanagement-ui-rhel10:1791460851
- libxml2-main-2.15.4-0.1.hum1
- RHSA-2026:71586
- RHSA-2026:71641
- RHSA-2026:71585
- RHSA-2026:72470
- RHSA-2026:72475
- RHSA-2026:72476
- RHSA-2026:79357
- RHSA-2026:64463
Official advisory · high-confidence parse· fetched 22 days ago·verify at source
Mitigation checklist
- To mitigate this, administrators should disable DTD processing and validation for untrusted documents within libxml2 parsers and restrict network access so only authorized users can submit XML data to the application. For robust defense-in-depth against buffer overflow exploitation, ensure the library and dependent applications are compiled with memory safety flags like stack canaries (-fstack-protector-strong) and bounds checking (_FORTIFY_SOURCE=2), while verifying that standard OS-level protections such as ASLR and Data Execution Prevention (NX/XD Bit) are active on the host system.
Official advisory · high-confidence parse· fetched 22 days ago·verify at source
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