What’s Vulnerable › Vulnerabilities

CVE-2026-40033: FreeRDP - Heap-buffer-overflow in gdi_CacheToSurface via rectangle validation bypass

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-05-26 · updated 2026-07-27
• Weakness: CWE-122

Description

FreeRDP before 3.26.0 contains a heap-buffer-overflow vulnerability in gdi_CacheToSurface that allows remote attackers to write out-of-bounds heap memory. The vulnerability occurs because rectangle validation clamps coordinates to UINT16_MAX but performs copy operations using unclamped cache entry dimensions, enabling malicious RDP servers to trigger large out-of-bounds writes and potentially achieve remote code execution or client crash.

Affected products

• FreeRDP: before 3.26.0 — fixed in 3.26.0

How to fix

Upgrade to a fixed version: FreeRDP 3.26.0. Check the vendor advisory for mitigations.

References

• https://github.com/FreeRDP/FreeRDP/commit/d7508ebcd82842a691ae4941e5104d14240a89ae
• https://github.com/FreeRDP/FreeRDP/pull/12713
• https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-p6r2-4hgm-m6ff
• https://www.vulncheck.com/advisories/freerdp-heap-buffer-overflow-in-gdi-cachetosurface-via-rectangle-validation-bypass
• https://access.redhat.com/errata/RHSA-2026:36203
• https://access.redhat.com/errata/RHSA-2026:46393
• https://access.redhat.com/security/cve/CVE-2026-40033
• https://bugzilla.redhat.com/show_bug.cgi?id=2481473
• https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-p6r2-4hgm-m6ff
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40033.json

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