Bug 2469203 (CVE-2026-42859)

Summary: CVE-2026-42859 neatvnc: neatvnc: Denial of Service via pre-authentication stack buffer overflow
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in neatvnc, a VNC server library. An unauthenticated remote attacker who can reach the VNC listening socket can send a crafted handshake with an oversized client RSA public key. This action causes a pre-authentication stack buffer overflow, leading to a denial of service due to a server crash.
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Bug Depends On: 2479809, 2479810    
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Description OSIDB Bzimport 2026-05-11 18:03:26 UTC 
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.