CVE-2026-91961VulnerabilityPublished 15 Sep 2026Updated 23 Sep 2026

FreeRDP before 3.31.0 contains a denial-of-service vulnerability in the URBDRC control-transfer request path that fails to validate OutputBufferSize before forwarding to the libusb backend

Affects freerdpSource GCVE Database

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Not known to be exploited · CVSS 6.5 Medium · fixed in 3.31.0+dfsg-0ubuntu0.24.04.1 : update freerdp when convenient.

Data as of 5 Nov 2026, 23:24 UTC

CVSS 3.1 base score

6.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 31% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.31.0+dfsg-0ubuntu0.24.04.1, 3.31.0+dfsg-0ubuntu0.26.04.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 15 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade the Ubuntu freerdp3 to 3.31.0+dfsg-0ubuntu0.24.04.1 (package) or 3.31.0+dfsg-0ubuntu0.26.04.1 (package).

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSfreerdp3`pkg:deb/ubuntu/freerdp3?arch=source&distro=resolute`Other threats	Affected <3.31.0+dfsg-0ubuntu0.26.04.1	Fixed in 3.31.0+dfsg-0ubuntu0.26.04.1
Ubuntu 24.04 LTSfreerdp3`pkg:deb/ubuntu/freerdp3?arch=source&distro=noble`Other threats	Affected <3.31.0+dfsg-0ubuntu0.24.04.1	Fixed in 3.31.0+dfsg-0ubuntu0.24.04.1
Ubuntu Pro 24.04 LTSfreerdp2`pkg:deb/ubuntu/freerdp2?arch=source&distro=esm-apps/noble`Other threats	Affected 2.10.0+dfsg1-1.1ubuntu1 – 2.11.5+dfsg1-1ubuntu0.1~esm6 12 affected builds	Fixed in–
Ubuntu 22.04 LTSfreerdp2`pkg:deb/ubuntu/freerdp2?arch=source&distro=jammy`Other threats	Affected 2.3.0+dfsg1-2build1 – 2.6.1+dfsg1-3ubuntu2.11 23 affected builds	Fixed in–
Ubuntu Pro 20.04 LTSfreerdp2`pkg:deb/ubuntu/freerdp2?arch=source&distro=esm-infra/focal`Other threats	Affected 2.0.0~git20190204.1.2693389a+dfsg1-1 – 2.6.1+dfsg1-0ubuntu0.20.04.2+esm4 17 affected builds	Fixed in–
Ubuntu Pro 18.04 LTSfreerdp2`pkg:deb/ubuntu/freerdp2?arch=source&distro=esm-infra/bionic`Other threats	Affected 2.0.0~git20170725.1.1648deb+dfsg1-1 – 2.2.0+dfsg1-0ubuntu0.18.04.4+esm6 19 affected builds	Fixed in–

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

AI-suggested

A patch is available for this vulnerability. Users should apply the official updates provided for the affected FreeRDP versions to remediate the issue. No additional mitigation steps are indicated by the vendor advisory.

Description

FreeRDP before 3.31.0 contains a denial-of-service vulnerability in the URBDRC control-transfer request path that fails to validate OutputBufferSize before forwarding to the libusb backend. A malicious RDP server can send a control-transfer request with OutputBufferSize set to 65536, triggering a reachable assertion that terminates the client process.

Impact

The vulnerability impacts availability by causing the control-transfer path to abort when the OutputBufferSize assertion is triggered. There is no impact on confidentiality or integrity. Exploitation requires user interaction but no privileges. The vulnerability can be exploited remotely over the network.

Summary

CVE-2026-91961 describes a vulnerability in FreeRDP where the URBDRC/libusb control-transfer path aborts due to a reachable assertion on OutputBufferSize. This causes an availability impact by potentially terminating the process or connection unexpectedly. The vulnerability affects numerous FreeRDP versions, including specific Ubuntu package releases. The CVSS 3.1 vector indicates network attack vector, low attack complexity, no privileges required, user interaction required, unchanged scope, no confidentiality or integrity impact, and high availability impact. There are no known exploits in the wild. A patch is available to remediate this issue.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 23 Sep 2026, 16:49 UTC

Technical details

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