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CVE-2026-44041— UltraVNC vncWc2Mb calls wcslen() before validating that the wide string is NUL-terminated

Quick assessment

Affected
uvnc UltraVNC
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.

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，该漏洞源于宽字符串到多字节转换辅助函数中存在越界读取，vncWc2Mb()函数在边界检查前将调用者提供的WCHAR指针传递给wcslen()，可能导致相邻内存区域的信息泄露或进程崩溃。

CVSS 4.3 · Medium EPSS 0.41% · P33

Affected Version Matrix 1

VendorProduct Version RangeStatus
uvnc UltraVNC ≤ 1.8.2.2 affected
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I. Basic Information for CVE-2026-44041

Vulnerability Information
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Vulnerability Title
UltraVNC vncWc2Mb calls wcslen() before validating that the wide string is NUL-terminated
Source: CVE Program / CVE List V5
Vulnerability Description
UltraVNC through 1.8.2.2 contains an out-of-bounds read in the wide-string to multibyte conversion helper. In rfb/dh.cpp:204, the vncWc2Mb() function passes a caller-supplied WCHAR pointer to wcslen() before any bounds check. If the caller provides a wide-character buffer that is not properly NUL-terminated, wcslen() reads past the end of the buffer until it encounters a NUL wchar, resulting in an out-of-bounds read. Under typical Win32 API usage this requires an abnormal caller contract. Impact is limited to a potential information disclosure from adjacent memory regions or a process crash (denial of service) if the over-read crosses a page boundary.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/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
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，该漏洞源于宽字符串到多字节转换辅助函数中存在越界读取，vncWc2Mb()函数在边界检查前将调用者提供的WCHAR指针传递给wcslen()，可能导致相邻内存区域的信息泄露或进程崩溃。
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-2026-44041

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III. Intelligence Information for CVE-2026-44041

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News Coverage for CVE-2026-44041 (1)

Vendor Pages for CVE-2026-44041 (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-2026-7829 7.2 HIGH UltraVNC repeater authenticated out-of-bounds write in rule parser via oversized token
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-2026-44042 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-125

V. Comments for CVE-2026-44041

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