How severe is CVE-2026-91955?

No CVSS score has been assigned to CVE-2026-91955 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-91955?

Affected package information for CVE-2026-91955 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2026-91955?

Upgrade the affected component to the fixed release for CVE-2026-91955, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.

How do I detect CVE-2026-91955 in my code and dependencies?

Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

How do I mitigate CVE-2026-91955 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-91955 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-91955 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-91955?

CVE-2026-91955 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 46th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-91955?

CVE-2026-91955 is classified as CWE-369 (CWE-369). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-91955 published, and has it been updated?

CVE-2026-91955 was published on September 15, 2026 and was last updated on September 26, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2026-91955: freerdp

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-91955.

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs46th percentile — riskier than 46% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Description

FreeRDP before 3.31.0 fails to validate client-supplied DesktopWidth and DesktopHeight values during GCC negotiation, allowing remote attackers to crash the server. Attackers can send crafted RDP packets with zero or oversized dimensions to trigger division-by-zero or assertion failures in multifragment update capability calculations, terminating the server process.

Affected Products

1 product · 1 configurations

Application

freerdpfreerdp

< 3.31.0

range

Detection & mitigation playbook

Vulnerability

Detect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Fix
Upgrade the affected component to the fixed release for CVE-2026-91955, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Workaround published by Red Hat

To reduce exposure, restrict network access to the FreeRDP server to trusted clients only. Configure firewall rules to limit incoming connections to the RDP port (typically 3389) from known and authorized IP addresses or subnets. If the FreeRDP server is not essential, consider disabling the service to prevent exploitation. Any changes to firewall rules or service status may require a service restart to take effect.

Source: Red Hat security advisory for CVE-2026-91955 (CC BY 4.0)

Frequently Asked Questions

FreeRDP before 3.31.0 fails to validate client-supplied DesktopWidth and DesktopHeight values during GCC negotiation, allowing remote attackers to crash the server. Attackers can send crafted RDP packets with zero or oversized dimensions to trigger division-by-zero or assertion failures in multifragment update capability calculations, terminating the server process.

O3 Security · Impact-Aware SCA

Is CVE-2026-91955 in your dependencies?

Find it across , including transitive dependencies.

Scan my dependencies How O3 SCA works

CVE-2026-91955 — freerdp