What’s Vulnerable › Vulnerabilities

CVE-2026-23533: FreeRDP has heap-buffer-overflow in clear_decompress_residual_data

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-01-19 · updated 2026-07-15
• Weakness: CWE-122

Description

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to version 3.21.0, a client-side heap buffer overflow occurs in the RDPGFX ClearCodec decode path when maliciously crafted residual data causes out-of-bounds writes during color output. A malicious server can trigger a client‑side heap buffer overflow, causing a crash (DoS) and potential heap corruption with code‑execution risk depending on allocator behavior and surrounding heap layout. Version 3.21.0 contains a patch for the issue.

Affected products

• FreeRDP: before 3.21.0 — fixed in 3.21.0

How to fix

Upgrade to a fixed version: FreeRDP 3.21.0. Check the vendor advisory for mitigations.

References

• https://github.com/FreeRDP/FreeRDP/blob/38514dfa5813aa945a86cfbcec279033f8394468/libfreerdp/codec/clear.c#L268-L281
• https://github.com/FreeRDP/FreeRDP/blob/38514dfa5813aa945a86cfbcec279033f8394468/libfreerdp/codec/clear.c#L336
• https://github.com/FreeRDP/FreeRDP/releases/tag/3.21.0
• https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-32q9-m5qr-9j2v
• https://access.redhat.com/errata/RHSA-2026:2048
• https://access.redhat.com/errata/RHSA-2026:2081
• https://access.redhat.com/errata/RHSA-2026:2222
• https://access.redhat.com/errata/RHSA-2026:2714
• https://access.redhat.com/errata/RHSA-2026:2736
• https://access.redhat.com/errata/RHSA-2026:2770
• https://access.redhat.com/errata/RHSA-2026:2824
• https://access.redhat.com/errata/RHSA-2026:2952

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