CVE-2026-44040
Açıklama (NVD)
UltraVNC through 1.8.2.2 uses a cryptographically weak pseudo-random number generator to produce VNC authentication challenge bytes. In rfb/vncauth.c:119-129, the vncRandomBytes() function seeds libc rand() with time(0) + getpid() + rand() and generates a 16-byte challenge. The combined seed space is approximately 31 bits (libc rand() internal state) and is entirely determined by publicly-observable values (wall-clock time and process ID). An attacker who can observe the authentication exchange can enumerate the seed space and predict the challenge within seconds, enabling forgery or offline brute-forcing of responses. Note: on Windows, the active code path may use vncEncryptBytes2.cpp which calls CryptGenRandom; reachability on shipped Windows binaries requires compile-graph verification and is under investigation.
Yayın: 01.07.2026 · Son değişiklik: 25.10.2026 · Zayıflık: CWE-338
CVSS 3.1 metrikleri
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
| Saldırı vektörü | Ağ (uzaktan) |
| Karmaşıklık | Düşük |
| Gereken yetki | Yok |
| Kullanıcı etkileşimi | Gerekmez |
| Kapsam | Değişmez |
| Gizlilik | Düşük |
| Bütünlük | Düşük |
| Erişilebilirlik | Yok |
Hesaplanan temel puan: 6.5. CVSS hesaplayıcıda incele