CVE-2026-44042
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.
Scoring
- Severity
- LOW
- CVSS base score
- 3.7
- CVSS vector
- CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
- EPSS probability
- 0.49%
- CWE
- CWE-193
- Published
- 2026-07-01
- Last modified
- 2026-07-09
Affected products
- uvnc UltraVNC
Weakness type
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