HighFix available
neatvnc — security advisory
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.
- Products
- neatvnc
- Affected versions
- 0.5.4+dfsg-1, 0.5.4+dfsg-2~exp1, 0.6.0+dfsg-1, 0.6.0+dfsg-2, 0.6.0+dfsg-3, 0.6.0+dfsg-4, 0.7.0+dfsg-1, 0.7.0+dfsg-1~exp1, 0.7.1+dfsg-1, 0.7.1+dfsg-2, 0.8.0+dfsg-1, 0.8.0+dfsg-2, 0.8.0+dfsg-3, 0.9.1+dfsg-1, 0.9.1+dfsg-1.1, 1.0.0+dfsg-1~exp1, 1.0.1+dfsg-1
- Fixed versions
- 0.9.1+dfsg-1.1
- CVEs
- CVE-2026-42859
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 17:48 UTC · Revision 2
Source evidence
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.
osv:DEBIAN-CVE-2026-42859
neatvnc
Fixed versions: Not specified
neatvnc
Fixed versions: Not specified
neatvnc
Fixed versions: 0.9.1+dfsg-1.1
Complete source record
{
"id": "346e204bde07c1e6b79e8aff6811ea256dc4d5d66c0290f4308c8f491df025ca",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-42859",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-42859",
"summary": "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.",
"evidence": "osv:DEBIAN-CVE-2026-42859",
"products": [
{
"name": {
"value": "neatvnc",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "0.5.4+dfsg-1",
"evidence": "/affected/0/versions"
},
{
"value": "0.5.4+dfsg-2~exp1",
"evidence": "/affected/0/versions"
},
{
"value": "0.6.0+dfsg-1",
"evidence": "/affected/0/versions"
},
{
"value": "0.6.0+dfsg-2",
"evidence": "/affected/0/versions"
},
{
"value": "0.6.0+dfsg-3",
"evidence": "/affected/0/versions"
},
{
"value": "0.6.0+dfsg-4",
"evidence": "/affected/0/versions"
},
{
"value": "0.7.0+dfsg-1",
"evidence": "/affected/0/versions"
},
{
"value": "0.7.0+dfsg-1~exp1",
"evidence": "/affected/0/versions"
},
{
"value": "0.7.1+dfsg-1",
"evidence": "/affected/0/versions"
},
{
"value": "0.7.1+dfsg-2",
"evidence": "/affected/0/versions"
},
{
"value": "0.8.0+dfsg-1",
"evidence": "/affected/0/versions"
},
{
"value": "0.8.0+dfsg-2",
"evidence": "/affected/0/versions"
},
{
"value": "0.8.0+dfsg-3",
"evidence": "/affected/0/versions"
},
{
"value": "0.9.1+dfsg-1",
"evidence": "/affected/0/versions"
},
{
"value": "0.9.1+dfsg-1.1",
"evidence": "/affected/0/versions"
},
{
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"evidence": "/affected/0/versions"
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{
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}
]
},
{
"name": {
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"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
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"evidence": "/affected/1/versions"
},
{
"value": "0.9.1+dfsg-1.1",
"evidence": "/affected/1/versions"
},
{
"value": "1.0.0+dfsg-1~exp1",
"evidence": "/affected/1/versions"
},
{
"value": "1.0.1+dfsg-1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
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"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
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"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "0.9.1+dfsg-1",
"evidence": "/affected/2/versions"
}
]
}
],
"severity": "high",
"structured": {
"id": "DEBIAN-CVE-2026-42859",
"aliases": [
"DEBIAN-CVE-2026-42859"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
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],
"package": {
"name": "neatvnc",
"purl": "pkg:deb/debian/neatvnc?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
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"0.5.4+dfsg-2~exp1",
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"0.6.0+dfsg-2",
"0.6.0+dfsg-3",
"0.6.0+dfsg-4",
"0.7.0+dfsg-1",
"0.7.0+dfsg-1~exp1",
"0.7.1+dfsg-1",
"0.7.1+dfsg-2",
"0.8.0+dfsg-1",
"0.8.0+dfsg-2",
"0.8.0+dfsg-3",
"0.9.1+dfsg-1",
"0.9.1+dfsg-1.1",
"1.0.0+dfsg-1~exp1",
"1.0.1+dfsg-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-42859.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "neatvnc",
"purl": "pkg:deb/debian/neatvnc?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"0.9.1+dfsg-1",
"0.9.1+dfsg-1.1",
"1.0.0+dfsg-1~exp1",
"1.0.1+dfsg-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-42859.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "0.9.1+dfsg-1.1"
}
]
}
],
"package": {
"name": "neatvnc",
"purl": "pkg:deb/debian/neatvnc?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"0.9.1+dfsg-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-42859.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-27T09:47:36.137831857Z",
"provider": "osv",
"upstream": [
"CVE-2026-42859"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-42859"
]
},
"related_cves": [
{
"value": "CVE-2026-42859",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 461255,
"published_at": "2026-05-11T18:16:36.4+00:00"
}