CVE-2026-44042 (GCVE-0-2026-44042)

Vulnerability from cvelistv5 – Published: 2026-07-01 03:33 – Updated: 2026-07-01 13:09
VLAI
Title
UltraVNC repeater wi_uudecode off-by-one in base64 decode boundary check
Summary
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.
Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
Assigner
References
URL Tags
https://uvnc.com/ vendor-advisory
https://github.com/ultravnc/UltraVNC product
Impacted products
Vendor Product Version
uvnc UltraVNC Affected: 0 , ≤ 1.8.2.2 (custom)
Create a notification for this product.
Credits
Arjun Basnet, Securin (arjun.basnet@securin.io)
Show details on NVD website
To clipboard 

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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