CVE-2026-42859 Details
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.
A pre-authentication stack buffer overflow vulnerability has been identified in Neat VNC versions prior to 0.9.6. This issue arises in the RSA-AES security type handler, where an unauthenticated remote attacker can send a crafted handshake with an oversized RSA public key. This oversized key causes a buffer overflow in a 1024-byte on-stack buffer while encrypting the server challenge, leading to a server crash and denial-of-service condition. The vulnerability can be exploited by any remote attacker who can reach the VNC listening socket.
Users can upgrade to Neat VNC version 0.9.6 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed May 11, 2026CISA-ADP
Assessed May 11, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/any1/neatvnc/commit/1f6cd6b75cc167fed3a19a9d1552a1f662f6b337 | [email protected] | Source CodeVendor |
| https://github.com/any1/neatvnc/security/advisories/GHSA-567c-gpv8-qh9h | [email protected] | AdvisoryRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-120 | Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Neat VNC | < 0.9.6 (semver) |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 11, 2026 | New CVE Received | [email protected] |