CVE-2026-91949: FreeRDP server versions before 3.31.0 contain a protocol negotiation bypass vulnerability that allows unauthen

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CRITICAL 9.3REMOTEUPGRADE

CVE-2026-91949 is a critical-severity flaw (CVSS 9.3) affecting freerdp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

FreeRDP server versions before 3.31.0 contain a protocol negotiation bypass vulnerability that allows unauthenticated attackers to establish RDSTLS connections despite server policy disabling them. Attackers can send incompatible protocol requests, receive negotiation failures, then complete TLS handshake and enter RDSTLS to bypass pre-authentication transport restrictions.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.3 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 53%)
CISA exploited list	No
Weakness	CWE-693
Published	2026-09-15
Last modified	2026-09-24

Publisher (CNA): VulnCheck · Vendor: freerdp

Last updated 2026-09-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-15 16:17 UTCPublished CVE record published
2026-09-24 12:14 UTCUpdated Record last modified

freerdp freerdp UPGRADE

Affected: >= 3.0.0 and < 3.31.0

Fixed in: 3.31.0

Safe to downgrade to: a release before 3.0.0

1. Check installed version

apt-cache policy freerdp || rpm -q freerdp || freerdp --version

2. UPGRADE to 3.31.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade freerdp

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade freerdp

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.0.0 (Debian / Ubuntu)

apt-cache madison freerdp sudo apt install freerdp=<VERSION_BEFORE_3.0.0> sudo apt-mark hold freerdp

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list freerdp sudo dnf downgrade freerdp-<VERSION_BEFORE_3.0.0> sudo dnf versionlock add freerdp

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-91949?

freerdp: upgrade to 3.31.0. Exact commands for each OS are on this page.

Is CVE-2026-91949 being exploited?

CVE-2026-91949 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-91949 affect?

CVE-2026-91949 affects freerdp. Severity is critical (CVSS 9.3). FreeRDP server versions before 3.31.0 contain a protocol negotiation bypass vulnerability that allows unauthenticated attackers to establish RDSTLS connections despite server policy disabling them. Attackers can send incompatible protocol r

How urgent is CVE-2026-91949?

Priority 54/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

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References

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