CVE-2026-42859
HighSummary
In the Neat VNC server library prior to version 0.9.6, a pre-authentication stack buffer overflow exists in the RSA-AES security type handler. An unauthenticated remote attacker who can reach the VNC listening socket can send a crafted handshake, leading to server crash.
Risk Assessment
This vulnerability can lead to denial of service through server crash, impacting service availability for users. Organizations should be aware of the risks associated with unauthorized access to the VNC server.
Recommendation
It is recommended to upgrade to version 0.9.6 or later to mitigate this vulnerability. Additionally, access to the VNC socket should be restricted to trusted IP addresses.
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Original NVD description (English source)
Neat VNC is a VNC server library. Prior to 0.9.6, a pre-authentication stack buffer overflow exists in neatvnc in the RSA-AES security type handler. An unauthenticated remote attacker who can reach the VNC listening socket can send a crafted security type 5 (RSA-AES) or security type 129 (RSA-AES-256) handshake with an oversized client RSA public key, causing rsa_aes_send_challenge in src/auth/rsa-aes.c to overflow a 1024-byte on-stack buffer when encrypting the server challenge. This results in at least a denial of service via server crash. This vulnerability is fixed in 0.9.6.