CVE-2026-22858

Critical

Description

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.20.1, global-buffer-overflow was observed in FreeRDP's Base64 decoding path. The root cause appears to be implementation-defined char signedness: on Arm/AArch64 builds, plain char is treated as unsigned, so the guard c <= 0 can be optimized into a simple c != 0 check. As a result, non-ASCII bytes (e.g., 0x80-0xFF) may bypass the intended range restriction and be used as an index into a global lookup table, causing out-of-bounds access. This vulnerability is fixed in 3.20.1.

SeverityCritical

CVSS9.1

Exploit probability—

ProductFreerdp

PublishedJan 14, 2026

First seenJan 14, 2026

Weakness typeCWE-125Out-of-bounds read CWE-758CWE-758

How to fix

Update

freerdp freerdp3.20.1 or later

Vendor advisories

Affected products

Product	Affected versions	Fixed in
freerdp freerdp	v < 3.20.1	3.20.1

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