FreeRDP: Heap out-of-bounds write in server NTLM authentication
Summary
FreeRDP versions from 2.0.0 before 3.32.0 contain a heap out-of-bounds write in the NTLM authentication path of FreeRDP servers and proxies that configure an NTLM hash callback. An unauthenticated attacker can send a crafted NTLM AUTHENTICATE_MESSAGE that causes a fixed 16-byte zero write beyond an allocated buffer. The advisory does not claim code execution or a password bypass, but the memory corruption may crash the service. Only FreeRDP-based server components are in scope.
Affected
- FreeRDP 2.0.0 up to but not including 3.32.0
- Only server or proxy deployments that set freerdp_peer::SspiNtlmHashCallback
Fixed in
- FreeRDP 3.32.0
- Distribution or vendor builds that include the fix
Workaround
Unknown. No vendor workaround was published.
- Do not expose FreeRDP-based RDP services directly to the internet; restrict access via VPN or gateway.
Exploitation
- CISA SSVC: exploitation none, not automatable
- Not listed as known exploited (CISA KEV)
- EPSS 0.00321 (low)
- No public proof of concept found in our research
Our recommendation
- Inventory FreeRDP use across hosts, products and vendor appliances.
- Confirm that no FreeRDP-based RDP server is directly reachable from the internet.
- Update to FreeRDP 3.32.0 or the vendor's fixed build.
- Ask vendors whether their products embed FreeRDP server code and which version.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- GitHub Security Advisory GHSA-cmgx-558f-vh67 github.com
- VulnCheck advisory: FreeRDP NTLM MIC offset heap out-of-bounds write www.vulncheck.com
- FreeRDP 3.32.0 release announcement www.freerdp.com
- Ubuntu security tracker CVE-2026-111880 ubuntu.com
- Tenable CVE-2026-111880 www.tenable.com
- Vulners CVE-2026-111880 (CVE List) vulners.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 13:36.
Original description (NVD)
FreeRDP versions from 2.0.0 before 3.32.0 contain a heap out-of-bounds write in the server hash-callback NTLM path that fails to validate the MIC offset. Unauthenticated attackers can send a crafted AUTHENTICATE_MESSAGE with a backward session-key offset and MIC offset to write 16 zero bytes beyond the allocation.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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