CVE-2026-55564
FreeRDP: Out-of-bounds read in glyph_cache_get via crafted glyph fragments
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.
INFO
Published Date :
Aug. 19, 2026, 6:16 p.m.
Last Modified :
Sept. 22, 2026, 7:44 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | MITRE-CVE | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update FreeRDP to version 3.27.0.
- Apply the patch provided by the vendor.
- Verify the updated version is installed.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-55564.
| URL | Resource |
|---|---|
| https://github.com/FreeRDP/FreeRDP/commit/c29324750e3cbcba8761f147b7a5235cc686930f | Patch |
| https://github.com/FreeRDP/FreeRDP/pull/12885 | Issue Tracking Patch |
| https://github.com/FreeRDP/FreeRDP/releases/tag/3.27.0 | Release Notes |
| https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-6xmj-pr98-cx4c | Exploit Mitigation Vendor Advisory |
| https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-6xmj-pr98-cx4c | Exploit Mitigation Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-55564 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-55564
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-55564 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-55564 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Sep. 22, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:freerdp:freerdp:*:*:*:*:*:*:*:* versions up to (excluding) 3.27.0 Added Reference Type GitHub, Inc.: https://github.com/FreeRDP/FreeRDP/commit/c29324750e3cbcba8761f147b7a5235cc686930f Types: Patch Added Reference Type GitHub, Inc.: https://github.com/FreeRDP/FreeRDP/pull/12885 Types: Issue Tracking, Patch Added Reference Type GitHub, Inc.: https://github.com/FreeRDP/FreeRDP/releases/tag/3.27.0 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-6xmj-pr98-cx4c Types: Exploit, Mitigation, Vendor Advisory Added Reference Type CISA-ADP: https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-6xmj-pr98-cx4c Types: Exploit, Mitigation, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 25, 2026
Action Type Old Value New Value Added Reference https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-6xmj-pr98-cx4c Added SSVC {'id': 'CVE-2026-55564', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-25T03:33:25.244841Z'} -
New CVE Received by [email protected]
Aug. 19, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'FreeRDP', 'product': 'FreeRDP', 'versions': [{'status': 'affected', 'version': '< 3.27.0'}]}] Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L Added CWE CWE-125 Added CWE CWE-193 Added Reference https://github.com/FreeRDP/FreeRDP/commit/c29324750e3cbcba8761f147b7a5235cc686930f Added Reference https://github.com/FreeRDP/FreeRDP/pull/12885 Added Reference https://github.com/FreeRDP/FreeRDP/releases/tag/3.27.0 Added Reference https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-6xmj-pr98-cx4c