FreeRDP RDPGFX CacheToSurface heap-buffer-overflow via clamped-rectangle validation bypass
FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.26.0, a malicious RDP server can trigger a heap-buffer-overflow write in the FreeRDP client by sending crafted RDPGFX PDUs. The bug is in gdi_CacheToSurface: it validates a destination rectangle that is clamped to UINT16_MAX, but then performs the copy using the original cacheEntry->width/height. This can cause a large out-of-bounds heap write and may lead to client crashes or code execution. This bug is reachable from a malicious RDP server, but only when the client has RDPGFX enabled. This vulnerability is fixed in 3.26.0.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-40033US | — | — | ||
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… | ||||
references
External citations — patches, advisories, analysis.
- https://access.redhat.com/errata/RHSA-2026:36203ADVISORY
- https://access.redhat.com/errata/RHSA-2026:46393ADVISORY
- https://access.redhat.com/security/cve/CVE-2026-44421ADVISORY
- https://bugzilla.redhat.com/show_bug.cgi?id=2483471REPORT
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44421.jsonADVISORY
- https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-p6r2-4hgm-m6ffADVISORY
- https://nvd.nist.gov/vuln/detail/CVE-2026-44421ADVISORY
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44421.jsonWEB
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