CVE-2026-55564
Received Received - Intake

Out-of-Bounds Read in FreeRDP

Publication date: 2026-08-19

Last updated on: 2026-08-19

Assigner: GitHub, Inc.

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.

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Meta Information

Published
2026-08-19
Last Modified
2026-08-19
Generated
2026-08-19
AI Q&A
2026-08-19
EPSS Evaluated
N/A
NVD
CVE-2026-55564
EUVD
EUVD-2026-62662

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
freerdp freerdp to 3.27.0 (inc)
freerdp freerdp to 3.27.0 (exc)

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
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CWE ID Description
CWE-193 A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.
CWE-125 The product reads data past the end, or before the beginning, of the intended buffer.

Attack-Flow Graph

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Executive Summary

This vulnerability is an out-of-bounds heap read in FreeRDP's glyph cache mechanism. A malicious RDP server can exploit it by sending crafted glyph fragments to trigger an incorrect bounds check in the glyph_cache_get function. The check uses > instead of >=, allowing an index equal to the cache size to read one slot past allocated memory. This may crash the client or leak adjacent heap data.

Detection Guidance

Detecting this vulnerability requires checking FreeRDP version and monitoring for crashes or heap corruption during RDP sessions. Use 'xfreerdp --version' or 'freerdp2 --version' to verify if your version is below 3.27.0. Monitor system logs for crashes or memory access violations during RDP connections.

Impact Analysis

The impact includes potential crashes (denial of service) when connecting to a malicious RDP server. It may also disclose adjacent heap data, posing a risk of information leakage. The attack requires no special privileges or user interaction beyond establishing an RDP connection.

Compliance Impact

This vulnerability may impact compliance with GDPR and HIPAA by potentially exposing sensitive data. An out-of-bounds heap read could leak adjacent memory, including sensitive information processed by the FreeRDP client. GDPR requires protecting personal data, and HIPAA mandates safeguarding protected health information. A crash or information leak could violate these regulations if exploited.

Mitigation Strategies

Immediately upgrade FreeRDP to version 3.27.0 or later. If upgrading is not possible, avoid connecting to untrusted RDP servers. Disable RDP services if not required. Monitor for suspicious activity or crashes in RDP clients.

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