any1 neatvnc up to 0.9.5 src/auth/rsa-aes.c rsa_aes_send_challenge buffer overflow

Summaryinfo

A vulnerability classified as critical has been found in any1 neatvnc up to 0.9.5. Impacted is the function rsa_aes_send_challenge of the file src/auth/rsa-aes.c. Performing a manipulation results in buffer overflow. This vulnerability is reported as CVE-2026-42859. The attack is possible to be carried out remotely. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in any1 neatvnc up to 0.9.5. It has been classified as critical. This affects the function rsa_aes_send_challenge of the file src/auth/rsa-aes.c. The manipulation with an unknown input leads to a buffer overflow vulnerability. CWE is classifying the issue as CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-42859 since 04/30/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available.

Upgrading to version 0.9.6 eliminates this vulnerability. Applying the patch 1f6cd6b75cc167fed3a19a9d1552a1f662f6b337 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• any1

Name

• neatvnc

Version

• 0.9.0
• 0.9.1
• 0.9.2
• 0.9.3
• 0.9.4
• 0.9.5

License

• open-source

Website

• Product: https://github.com/any1/neatvnc/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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