CVE-2026-55191
Heap buffer overflow in FreeRDP H.264 AVC444 may allow RCE via a malicious RDP server
Is CVE-2026-55191 being exploited?
Not confirmed. CVE-2026-55191 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.60% probability of exploitation in the next 30 days.
How severe is CVE-2026-55191?
CVE-2026-55191 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-55191?
Yes. A fix has been recorded for CVE-2026-55191. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-55191 affect?
CVE-2026-55191 affects FreeRDP < 3.27.0, Clients using libfreerdp/codec/h264 AVC444 H.264 backend, RDP clients built on affected FreeRDP releases. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-55191?
Upgrade FreeRDP to 3.27.0+, block untrusted RDP servers, or disable AVC444 H.264 decoder
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution via a malicious RDP server causing heap corruption from undersized buffer during AVC444 H.264 decoding.
Immediate action required
- affected< 3.27.0
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.