CVE-2026-44042: falha de baixa gravidade em uvnc UltraVNC
UltraVNC repeater wi_uudecode off-by-one in base64 decode boundary check
Publicada em · Atualizada em
Aviso por e-mail quando ela entrar no KEV, ganhar PoC pública ou subir de nota.
8Vexday Risk Score
Sem sinal de exploração. Nenhum artefato público de exploração conhecido até agora.
ssvc Trackcvss 3.7epss 0.5%
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.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Produtos afetados
uvnc · UltraVNCCVEs relacionadas — uvnc UltraVNC
No mesmo produto, das mais perigosas para as menos.
CVE-2026-7840CRITICALUltraVNC repeater HTTP server global buffer overflow via long URI (pre-auth RCE)EPSS 2.6%CVE-2026-7838HIGHUltraVNC viewer heap buffer overflow via integer overflow in RFB connection-failure reason lengthEPSS 1.9%CVE-2026-7828MEDIUMUltraVNC repeater integer overflow in win_log malloc leading to heap overflowEPSS 1.4%CVE-2026-7829HIGHUltraVNC repeater authenticated out-of-bounds write in rule parser via oversized tokenEPSS 0.9%CVE-2026-7831HIGHUltraVNC viewer off-by-one stack overflow in ServerInit desktop name parsingEPSS 0.7%CVE-2026-7839CRITICALUltraVNC repeater ships hardcoded default admin password allowing unauthenticated admin accessEPSS 0.7%