CVE-2026-22858: FreeRDP has a global-buffer-overflow in crypto_base64_decode

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-01-14 · updated 2026-07-15
Weakness: CWE-125

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.

Affected products

FreeRDP: before 3.20.1 — fixed in 3.20.1

How to fix

Upgrade to a fixed version: FreeRDP 3.20.1. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2026-22858 or the next vulnerability affects your stack