CVE-2026-55564

MEDIUM

5.4

CVSS v3

Description

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.27.0, the glyph_cache_get function in libfreerdp/cache/glyph.c checks whether index is greater than cache->number instead of greater than or equal to it. A malicious RDP server can use GLYPH_FRAGMENT_USE replay in update_process_glyph_fragments to make the default cache receive index 254 when cache->number is 254, reading one pointer beyond the entries array and dereferencing it as a glyph. This can crash the client and may disclose adjacent heap data. This issue is fixed in version 3.27.0.

CWE-125Out-of-bounds Read CWE-193

How to fix

Remediation Available

freerdp3Ubuntu

Fixed in:3.30.0+dfsg-0ubuntu0.24.04.1USN-8561-1

freerdp3-x11Ubuntu

Fixed in:3.30.0+dfsg-0ubuntu0.24.04.1USN-8561-1

libfreerdp3-3Ubuntu

Fixed in:3.30.0+dfsg-0ubuntu0.24.04.1USN-8561-1

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityNone

AvailabilityLow

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

Exploit Intelligence

0.27%probability of exploitation in 30 days

18thpercentile

Low risk: more likely to be exploited than 18% of all known CVEs.

References

Other references4

Related Vulnerabilities

Other CWE-125 (Out-of-bounds Read) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2014-0160	High	7.5	100%	KEV	Fix
CVE-2025-5777	High	7.5	100%	KEV + Ransom	Fix
CVE-2021-4034	High	7.8	95%	KEV + Ransom	Fix
CVE-2020-8794	Critical	9.8	89%	-	Fix
CVE-2023-49285	High	8.6	89%	-	Fix
CVE-2023-21769	High	7.5	89%	-	Fix

Common questions

How do I fix CVE-2026-55564?

Published advisories record a fix for 3 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.

Is CVE-2026-55564 being actively exploited?

Not that we know of. CVE-2026-55564 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.27% is the estimated probability that it will be exploited in the next 30 days. That is higher than 18% of all scored CVEs.

How severe is CVE-2026-55564?

CVE-2026-55564 has a CVSS v3 base score of 5.4, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2026-55564 affect?

Published advisories record a fix for freerdp3 (Ubuntu), freerdp3-x11 (Ubuntu), libfreerdp3-3 (Ubuntu). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-25.