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CVE-2026-67303VulnerabilityPublished Updated

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

Affects freerdpSource GCVE Database

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Not known to be exploited · CVSS 4.3 Medium : upgrade to 3.29.0 when convenient.

Data as of 31 Oct 2026, 08:20 UTC

CVSS 3.1 base score
4.3Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 36% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.29.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 1 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade freerdp/FreeRDP to 3.29.0.

Affected software

ProductAffectedFixed in
GitHubfreerdp/FreeRDPpkg:github/freerdp/FreeRDPOther threatsAffected
  • <3.29.0
Fixed in
  • 3.29.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in FreeRDP version 3.29.0. Users should upgrade to version 3.29.0 or later to remediate this vulnerability. No vendor advisory was provided to indicate alternative mitigations or temporary fixes.

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).

References

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