CVE-2026-42859

Name	CVE-2026-42859
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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1136644

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
neatvnc (PTS)	bookworm	0.5.4+dfsg-1	vulnerable
	forky, sid, trixie	0.9.1+dfsg-1	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
neatvnc	source	(unstable)	(unfixed)			1136644

Notes

[trixie] - neatvnc <no-dsa> (Minor issue)
[bookworm] - neatvnc <no-dsa> (Minor issue)
https://github.com/any1/neatvnc/security/advisories/GHSA-567c-gpv8-qh9h
https://github.com/any1/neatvnc/commit/1f6cd6b75cc167fed3a19a9d1552a1f662f6b337 (v1.0.0)