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CVE-2026-107611— Out-of-bounds read in TightVNC Viewer ZRLE palette decoding

Quick assessment

Affected
GlavSoft TightVNC
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.

在 GlavSoft TightVNC Viewer for Windows 2.8.88 之前的版本中，ZRLE 解码器存在一个越界读取漏洞。攻击者可通过提供恶意或已被控制的 VNC 服务器，向客户端发送 ZRLE 编码的图块（tiles），其调色板索引值超过声明的调色板大小，从而读取调色板分配区域之外的堆内存，导致 VNC 查看器崩溃。 和 函数在使用攻击者提供的索引值查找颜色时，未对该索引与调色板大小进行有效性验证。这会导致越界堆数据被复制到帧缓冲区（造成显示乱码），或者因非法内存访问引发读取错误，从而终止查

CVSS 7.1 · High

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution
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I. Basic Information for CVE-2026-107611

Vulnerability Information
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Vulnerability Title
Out-of-bounds read in TightVNC Viewer ZRLE palette decoding
Source: CVE Program / CVE List V5
Vulnerability Description
An out-of-bounds read vulnerability in the ZRLE decoder of GlavSoft TightVNC Viewer for Windows before 2.8.88 allows a malicious or compromised VNC server to read heap memory beyond the palette allocation and crash the viewer by sending ZRLE-encoded tiles whose palette indices exceed the declared palette size. readPaletteRleTile() and readPackedPaletteTile() use the attacker-supplied index to look up colours without validating it against the palette size; out-of-bounds heap data is copied into the framebuffer (garbled display) or the read faults, terminating the viewer.
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:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
GlavSoft TightVNC 0 ~ 2.8.88 -

II. Public POCs for CVE-2026-107611

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III. Intelligence Information for CVE-2026-107611

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Vendor Pages for CVE-2026-107611 (1)

Other References for CVE-2026-107611 (1)

Same Patch Batch · GlavSoft · 2026-10-08 · 5 CVEs total

CVE-2026-107612 7.8 HIGH World-accessible IPC shared memory with predictable name in TightVNC Server
CVE-2026-107615 7.8 HIGH DLL search order hijacking via screenhooks libraries in TightVNC Server
CVE-2026-107614 6.1 MEDIUM Integer underflow in TightVNC Server cursor shape trimming leads to out-of-bounds read
CVE-2026-107613 5.9 MEDIUM NULL pointer dereference in TightVNC Server Win8ScreenDriver after failed DXGI re-initiali

IV. Related Vulnerabilities

Same product: TightVNC
Same vendor: GlavSoft
Same weakness: CWE-125

V. Comments for CVE-2026-107611

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