Vulnerability · Published Aug 1, 2026 · Assigned by VulnCheck

CVE-2026-67303FreeRDP before 3.29.0 Denial of Service via serial DeviceControl

Medium 4.3

In plain English

A medium-severity security flaw in FreeRDP from FreeRDP. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 36% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.3Medium

Exploit odds (30 days)0.4%top 63.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

FreeRDP before 3.29.0 contains a reachable assertion (WINPR_ASSERT(OutputBufferLength == BytesReturned)) in serial_process_irp_device_control() in channels/serial/client/serial_main.c. When serial device redirection is enabled and a server-controlled IRP_MJ_DEVICE_CONTROL request specifies an unsupported IOCTL with a non-zero OutputBufferLength, CommDeviceIoControl() can fail with BytesReturned = 0, causing the mismatch to trigger the assertion and abort the client process (denial of service).

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	freerdp2	no fix listed	DEBIAN-CVE-2026-67303
Debian:13	freerdp3	no fix listed	DEBIAN-CVE-2026-67303
Debian:14	freerdp3	3.29.0+dfsg-1	DEBIAN-CVE-2026-67303
Ubuntu:22.04:LTS	freerdp2	no fix listed	UBUNTU-CVE-2026-67303
Ubuntu:24.04:LTS	freerdp3	3.30.0+dfsg-0ubuntu0.24.04.1	UBUNTU-CVE-2026-67303
Ubuntu:26.04:LTS	freerdp3	3.30.0+dfsg-0ubuntu0.26.04.1	UBUNTU-CVE-2026-67303

Affected products (as reported)

Vendor	Product	Versions
FreeRDP	FreeRDP	0 – before 3.29.0

Weakness: CWE-617 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

References

GitHub Security Advisory (GHSA-pfxq-3qmw-8vjx) vendor-advisory
Patch Commit patch
Patch Commit patch
VulnCheck Advisory: FreeRDP before 3.29.0 Denial of Service via serial DeviceControl third-party-advisory