CVE-2026-44041

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.

CVSS v3.1 Score

4.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

EPSS — Exploit Prediction

0.0026

Probability of exploitation

0.17%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-125 Out-of-bounds Read

Affected Products

Vendor	Product	Versions
uvnc	ultravnc	< 1.8.2.2

References

Other References

https://github.com/ultravnc/UltraVNC https://uvnc.com/

Frequently Asked Questions

What is CVE-2026-44041? +

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. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2026-44041? +

CVE-2026-44041 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0026, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-44041? +

CVE-2026-44041 affects products from uvnc, specifically: ultravnc. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-44041? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-29013

libcoap contains out-of-bounds read vulnerabilities in OSCORE Appendix B.2 CBOR unwrap handling where get_byte_inc() in src/oscore/oscore_cbor.c relies solely on assert() …

CVE-2026-3508

An Out-of-bounds Read vulnerability in the IOCTL handler in ASUS System Control Interface allows a local user to cause system …

CVE-2025-48520

An improper input validation vulnerability within the AMD Platform Management Framework (PMF) driver can allow a local attacker to read …

CVE-2026-3894

Out-of-bounds Read vulnerability in RTI Connext Professional (Core Libraries) allows Overread Buffers.This issue affects Connext Professional: from 7.4.0 before 7.7.0, …

CVE-2025-4098

Horner Automation Cscape version 10.0 (10.0.415.2) SP1 is vulnerable to an out-of-bounds read vulnerability that could allow an attacker to …

CVE-2025-49849

An Out-of-bounds Read vulnerability exists within the parsing of PRJ files. The issues result from the lack of proper validation …