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CVE-2026-55564— FreeRDP: Out-of-bounds read in glyph_cache_get via crafted glyph fragments

Quick assessment

Affected
FreeRDP FreeRDP
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

FreeRDP是FreeRDP组织开源的一款远程桌面协议(RDP)的实现。 FreeRDP 3.27.0之前版本存在安全漏洞，该漏洞源于glyph_cache_get函数对索引的边界检查不当（应使用大于等于而非大于），可能允许恶意RDP服务器利用GLYPH_FRAGMENT_USE重放导致越界读取，造成客户端崩溃或泄露相邻堆数据。

CVSS 5.4 · Medium EPSS 0.27% · P18

Affected Version Matrix 1

VendorProduct Version RangeStatus
FreeRDP FreeRDP < 3.27.0 affected
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I. Basic Information for CVE-2026-55564

Vulnerability Information
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Vulnerability Title
FreeRDP: Out-of-bounds read in glyph_cache_get via crafted glyph fragments
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
Source: CVE Program / CVE List V5
Vulnerability Title
FreeRDP 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
FreeRDP是FreeRDP组织开源的一款远程桌面协议(RDP)的实现。 FreeRDP 3.27.0之前版本存在安全漏洞，该漏洞源于glyph_cache_get函数对索引的边界检查不当（应使用大于等于而非大于），可能允许恶意RDP服务器利用GLYPH_FRAGMENT_USE重放导致越界读取，造成客户端崩溃或泄露相邻堆数据。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
FreeRDP FreeRDP < 3.27.0 -

II. Public POCs for CVE-2026-55564

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III. Intelligence Information for CVE-2026-55564

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Patches & Fixes for CVE-2026-55564 (2)

Vendor Advisories for CVE-2026-55564 (1)

Vendor Pages for CVE-2026-55564 (1)

Same Patch Batch · FreeRDP · 2026-08-19 · 9 CVEs total

CVE-2026-55191 8.7 HIGH FreeRDP: Heap-buffer-overflow write in AVC444 YUV buffer allocation
CVE-2026-55194 8.7 HIGH FreeRDPHeap-buffer-overflow write in TS Gateway RPC RESPONSE reassembly due to alloc_hint
CVE-2026-55193 8.7 HIGH FreeRDP: Heap-buffer-overflow write in TS Gateway RPC fragment receive due to uncapped bin
CVE-2026-63633 7.7 HIGH FreeRDP: Heap buffer overflow in Opus audio decode (`freerdp_dsp_decode_opus` resizes the
CVE-2026-55192 7.2 HIGH FreeRDP: Out-of-bounds read in H.264 YUV-to-RGB conversion due to decoder/surface dimensio
CVE-2026-63652 7.1 HIGH FreeRDP: Double-free of `client_formats` in the rdpsnd server channel on a malformed Clien
CVE-2026-63117 6.5 MEDIUM FreeRDP: Denial of service through ADPCM frame size calculation
CVE-2026-55648 6.1 MEDIUM FreeRDP: Integer Overflow in `freerdp_image_copy_from_icon_data` Bypasses Bounds Check

IV. Related Vulnerabilities

Same product: FreeRDP
Same vendor: FreeRDP
Same weakness: CWE-125

V. Comments for CVE-2026-55564

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