# CVE-2026-44042

## Summary

- **CVE ID:** CVE-2026-44042
- **Severity:** LOW
- **CVSS Score:** 3.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L)
- **CWE:** CWE-193
- **Published:** Jul 1, 2026
- **Last Modified:** Jul 9, 2026

## Description

UltraVNC repeater through 1.8.2.2 contains an off-by-one error in the Base64 decode helper used for HTTP Basic authentication. In repeater/webgui/webutils.c:817, the wi_uudecode() function checks whether the input length exceeds the output buffer with a strict greater-than comparison (>), while the correct check should be greater-than-or-equal (>=). When strlen(authdata) equals sizeof(decode), the decoded output length (approximately 3/4 of input) does not overflow the buffer in current practice because the outer HTTP request bounds constrain the Authorization header. However, the defective check leaves a latent off-by-one condition that could become exploitable if the buffering constraints change. The current risk is limited to a one-byte write at the boundary of a 1024-byte stack buffer under constrained conditions.

## Affected Products

- uvnc — UltraVNC (0)

## References

- [CNA](https://uvnc.com/)
- [CNA](https://github.com/ultravnc/UltraVNC)
- [CNA](https://www.securin.io/zero-days/cve-2026-44042-wi-uudecode-off-by-one-bounded-ultravnc-repeater)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.49%
- **EPSS Percentile:** 40.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._