CVE-2026-6210: Type confusion and heap-buffer-overflow in Qt SVG marker handling causing application crash

Severity: high (CVSS 8.7 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-06 · updated 2026-07-29
Weakness: CWE-122

Description

A type confusion vulnerability in Qt SVG allows an attacker to cause an application crash via a crafted SVG image. When processing SVG marker references, the renderer retrieves a node by its id attribute and casts it to QSvgMarker* without verifying the node type. A non-marker element (such as a <line> element) that references itself as a marker triggers an out-of-bounds heap read due to the object size difference between QSvgLine and QSvgMarker, followed by an endless recursion that bypasses the marker recursion guard through incorrect virtual dispatch. The result is an application crash (denial of service). This issue affects Qt SVG: from 6.7.0 before 6.8.8, from 6.9.0 before 6.11.1.

Affected products

Qt: from 6.7.0 before 6.8.8; from 6.9.0 before 6.11.1 — fixed in 6.11.1, 6.8.8

How to fix

Upgrade to a fixed version: Qt 6.11.1, 6.8.8. Check the vendor advisory for mitigations.

References

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