Vulnerability in Neat VNC (CVE-2026-42859)
Summary
Vulnerability in Neat VNC (CVE-2026-42859). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 0.9.6 or later.
Original description
The description as published by the source.
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: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-42859 has been found in Neat VNC.
Risk of unauthorized operations or information disclosure.
What to do: upgrade Neat VNC to 0.9.6 or later.
If unsure, ask your IT team or search "Neat VNC CVE-2026-42859" on the vendor's site.
CVE-2026-42859 (Neat VNC) — CWE-120
Patched: 0.9.6 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-120) exists in Neat VNC.
Check the vendor advisory for the affected versions of Neat VNC.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 0.9.6.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Neat VNC を使っているサービスとバージョンを洗い出す。
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2Apply patch patch
Upgrade Neat VNC to 0.9.6ステージング環境で 0.9.6 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-42859 neatvnc
- Ubuntu UBUNTU-CVE-2026-42859 neatvnc
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- patch github.com