CVE-2026-91949Public exploitNetwork attack vectorHinoki check available

Pre-authentication RDSTLS exposure via failure-bit confusion

Published Sep 15, 2026 · Updated Sep 15, 2026

Protocol negotiation bypass in FreeRDP server 3.0.0 through 3.30.0 allows remote attackers to establish disallowed RDSTLS connections. The server stores a negotiation-failure sentinel and failure code in SelectedProtocol, then tests that combined value as a protocol bitmask and dispatches it as RDSTLS. Network access to an NLA-only RDP listener is sufficient; the resulting connection bypasses the pre-authentication transport restriction without authenticating the peer.

CVSS severity9.3
Critical
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Protocol negotiation bypass in FreeRDP server 3.0.0 through 3.30.0 allows remote attackers to establish disallowed RDSTLS connections. The server stores a negotiation-failure sentinel and failure code in SelectedProtocol, then tests that combined value as a protocol bitmask and dispatches it as RDSTLS. Network access to an NLA-only RDP listener is sufficient; the resulting connection bypasses the pre-authentication transport restriction without authenticating the peer.

The record

CVE
CVE-2026-91949
Published
Sep 15, 2026
Updated
Sep 15, 2026
Vendor
FreeRDP
Product
FreeRDP
Classifications
CWE-693, CWE-755
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.0.0 <3.31.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

FreeRDP · FreeRDPversion=3.0.0 <3.31.0

Published CVSS scores

9.3FreeRDP GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-693Protection Mechanism Failure
CWE-755Improper Handling of Exceptional Conditions

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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