PT-2026-54479 · Uvnc · Ultravnc
Published
2026-07-01
·
Updated
2026-07-01
·
CVE-2026-44042
CVSS v3.1
3.7
Low
| Vector | AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L |
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.
Fix
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Weakness Enumeration
Related Identifiers
Affected Products
Ultravnc