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Description

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.

PUBLISHED Reserved 2026-04-30 | Published 2026-05-11 | Updated 2026-05-11 | Assigner GitHub_M




HIGH: 8.1CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U

Problem types

CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

Product status

< 0.9.6
affected

References

github.com/...eatvnc/security/advisories/GHSA-567c-gpv8-qh9h

github.com/...ommit/1f6cd6b75cc167fed3a19a9d1552a1f662f6b337

cve.org (CVE-2026-42859)

nvd.nist.gov (CVE-2026-42859)

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