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

OR
          *cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:* versions up to (including) 1.8.2.2

securin: https://github.com/ultravnc/UltraVNC Types: Product

securin: https://uvnc.com/ Types: Product, Release Notes

{"timestamp":"2026-07-01T13:08:54.695763Z","id":"CVE-2026-44042","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}

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.

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

CWE-193

https://github.com/ultravnc/UltraVNC

https://uvnc.com/

[{"vendor":"uvnc","product":"UltraVNC","defaultStatus":"unaffected","modules":["repeater"],"versions":[{"version":"0","lessThanOrEqual":"1.8.2.2","versionType":"custom","status":"affected"}]}]