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CVE-2026-7829— UltraVNC repeater authenticated out-of-bounds write in rule parser via oversized token

Quick assessment

Affected
uvnc UltraVNC
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

ultravnc是UltraVNC组织开源的一款用于Windows平台的开源远程终端控制软件。 UltraVNC 1.8.2.2及之前版本存在缓冲区错误漏洞，该漏洞源于允许/拒绝规则解析器中的越界写入问题，在strncpy_s复制规则令牌后未限制长度，导致NUL终止符写入超出栈分配数组边界，破坏相邻栈数据，可能允许已获管理员凭据的攻击者在中继主机上执行代码。

CVSS 7.2 · High EPSS 0.85% · P57

Affected Version Matrix 1

VendorProduct Version RangeStatus
uvnc UltraVNC ≤ 1.8.2.2 affected
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I. Basic Information for CVE-2026-7829

Vulnerability Information
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Vulnerability Title
UltraVNC repeater authenticated out-of-bounds write in rule parser via oversized token
Source: CVE Program / CVE List V5
Vulnerability Description
UltraVNC repeater through 1.8.2.2 contains a post-authentication out-of-bounds write in the allow/deny rule parser. In repeater/webgui/settings.c:225-272, after strncpy_s copies a rule token into temp1[rule1] (25-byte destination) or temp2/temp3 (16-byte destination), the code unconditionally writes a NUL terminator at temp1[rule1][len] = 0 without clamping len to the destination size. When an authenticated administrator saves a rule with a token length equal to or greater than the destination size, the NUL byte is written one or more bytes past the end of the stack-allocated array, corrupting adjacent stack data. An attacker who has obtained admin credentials (including via CVE-2026-7839 default password) can trigger this to gain code execution on the repeater host.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5
Vulnerability Title
UltraVNC 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
ultravnc是UltraVNC组织开源的一款用于Windows平台的开源远程终端控制软件。 UltraVNC 1.8.2.2及之前版本存在缓冲区错误漏洞，该漏洞源于允许/拒绝规则解析器中的越界写入问题，在strncpy_s复制规则令牌后未限制长度，导致NUL终止符写入超出栈分配数组边界，破坏相邻栈数据，可能允许已获管理员凭据的攻击者在中继主机上执行代码。
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
uvnc UltraVNC 0 ~ 1.8.2.2 -

II. Public POCs for CVE-2026-7829

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Qwen3.6-35B-A3B · 9806 chars
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III. Intelligence Information for CVE-2026-7829

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News Coverage for CVE-2026-7829 (1)

Vendor Pages for CVE-2026-7829 (1)

Same Patch Batch · uvnc · 2026-07-01 · 10 CVEs total

CVE-2026-7840 9.8 CRITICAL UltraVNC repeater HTTP server global buffer overflow via long URI (pre-auth RCE)
CVE-2026-7839 9.1 CRITICAL UltraVNC repeater ships hardcoded default admin password allowing unauthenticated admin ac
CVE-2026-7838 8.8 HIGH UltraVNC viewer heap buffer overflow via integer overflow in RFB connection-failure reason
CVE-2026-7831 7.5 HIGH UltraVNC viewer off-by-one stack overflow in ServerInit desktop name parsing
CVE-2026-7830 7.4 HIGH UltraVNC MS-Logon II uses 64-bit Diffie-Hellman and seeded libc rand() enabling credential
CVE-2026-7828 5.3 MEDIUM UltraVNC repeater integer overflow in win_log malloc leading to heap overflow
CVE-2026-44040 4.8 MEDIUM UltraVNC vncauth.c uses time-seeded libc rand() to generate VNC authentication challenge b
CVE-2026-44041 4.3 MEDIUM UltraVNC vncWc2Mb calls wcslen() before validating that the wide string is NUL-terminated
CVE-2026-44042 3.7 LOW UltraVNC repeater wi_uudecode off-by-one in base64 decode boundary check

IV. Related Vulnerabilities

Same product: UltraVNC
Same vendor: uvnc
Same weakness: CWE-787

V. Comments for CVE-2026-7829

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