Medium severity · published Aug 1, 2026
CVE-2026-67303
FreeRDP before 3.29.0 Denial of Service via serial DeviceControl
4.3
CVSS
0.4%
EPSS
No
On KEV
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).
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 36% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FR
FreeRDP · FreeRDP
before 3.29.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-67303
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-67303
Patch
https://github.com/FreeRDP/FreeRDP/commit/1cc783d4c78bd2f66d3a8582dfe70a663d141444
Patch
https://github.com/FreeRDP/FreeRDP/commit/5370fb26fbf034ecd11d3026b6ad639b5fff493f
Mitigation
https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-pfxq-3qmw-8vjx
Patch
https://www.vulncheck.com/advisories/freerdp-before-denial-of-service-via-serial-devicecontrol
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