High
Security advisory
An issue was discovered in LibVNCServer before 0.9.13. libvncserver/ws_decode.c can lead to a crash because of unaligned accesses in hybiReadAndDecode.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2019-20840
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 12:29 UTC · Revision 1
Source evidence
An issue was discovered in LibVNCServer before 0.9.13. libvncserver/ws_decode.c can lead to a crash because of unaligned accesses in hybiReadAndDecode.
osv:CVE-2019-20840
Complete source record
{
"id": "609f568dd739ed9687007c4cd36c23e219cc40de800ed6a9867eea482fd4a960",
"url": "https://osv.dev/vulnerability/CVE-2019-20840",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2019-20840",
"summary": "An issue was discovered in LibVNCServer before 0.9.13. libvncserver/ws_decode.c can lead to a crash because of unaligned accesses in hybiReadAndDecode.",
"evidence": "osv:CVE-2019-20840",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2019-20840",
"aliases": [
"CVE-2019-20840"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/libvnc/libvncserver",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"last_affected": "0a70095271d845d16a3ed17354841b01f33963ad"
},
{
"fixed": "0cf1400c61850065de590d403f6d49e32882fd76"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:libvnc_project:libvncserver:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0"
},
{
"last_affected": "0.9.12"
}
],
"source": "CPE_RANGE"
},
{
"range": [
{
"fixed": "0cf1400c61850065de590d403f6d49e32882fd76"
}
],
"source": "REFERENCES_COMMIT"
}
]
}
}
],
"versions": [
"LibVNCServer-0.9.12",
"LibVNCServer-0.9.11",
"LibVNCServer-0.9.10",
"LibVNCServer-0.9.9",
"LibVNCServer-0.9.8",
"X11VNC_0_9_12",
"X11VNC_0_9_11",
"X11VNC_0_9_10",
"X11VNC_0_9_9",
"X11VNC_0_9_8",
"X11VNC_0_9_7",
"X11VNC_REL_0_9_6",
"X11VNC_REL_0_9_5",
"X11VNC_REL_0_9_4"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2019-20840.json",
"vanir_signatures": [
{
"id": "CVE-2019-20840-10709c66",
"digest": {
"length": 4063,
"function_hash": "180079713415210745791807162750284308920"
},
"source": "https://github.com/libvnc/libvncserver/commit/0cf1400c61850065de590d403f6d49e32882fd76",
"target": {
"file": "libvncserver/ws_decode.c",
"function": "hybiReadAndDecode"
},
"deprecated": false,
"signature_type": "Function",
"signature_version": "v1"
},
{
"id": "CVE-2019-20840-337dc46d",
"digest": {
"threshold": 0.9,
"line_hashes": [
"280535027786460026972189112772063445853",
"50701751959996758734036103654922009095",
"152558449667183412663568482169208692828",
"327930894662464802945272025504953063997",
"187881109947118880620593900587007315645",
"215302365506936472057092840460876039458",
"50659555013314031717534322792322098385",
"184898503279201702730802996537756075167",
"96434419174010811701165366566747251317",
"176232627971923197157543118542926500038"
]
},
"source": "https://github.com/libvnc/libvncserver/commit/0cf1400c61850065de590d403f6d49e32882fd76",
"target": {
"file": "libvncserver/ws_decode.c"
},
"deprecated": false,
"signature_type": "Line",
"signature_version": "v1"
}
],
"vanir_signatures_modified": "2026-10-20T13:42:59Z"
}
}
],
"modified": "2026-10-20T13:42:59.045128547Z",
"provider": "osv",
"references": [
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4F6FUH4EFK4NAP6GT4TQRTBKWIRCZLIY/",
"https://github.com/LibVNC/libvncserver/compare/LibVNCServer-0.9.12...LibVNCServer-0.9.13",
"https://usn.ubuntu.com/4434-1/",
"https://cert-portal.siemens.com/productcert/pdf/ssa-390195.pdf",
"https://github.com/LibVNC/libvncserver/commit/0cf1400c61850065de590d403f6d49e32882fd76"
],
"provider_metadata": {
"unresolved_ranges": [
{
"cpes": [
"cpe:2.3:o:siemens:simatic_itc1500_firmware:*:*:*:*:*:*:*:*"
],
"vendor_product": "siemens:simatic_itc1500_firmware",
"extracted_events": [
{
"range": [
{
"introduced": "3.0.0.0"
},
{
"fixed": "3.2.1.0"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:o:siemens:simatic_itc1500_pro_firmware:*:*:*:*:*:*:*:*"
],
"vendor_product": "siemens:simatic_itc1500_pro_firmware",
"extracted_events": [
{
"range": [
{
"introduced": "3.0.0.0"
},
{
"fixed": "3.2.1.0"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:o:siemens:simatic_itc1900_firmware:*:*:*:*:*:*:*:*"
],
"vendor_product": "siemens:simatic_itc1900_firmware",
"extracted_events": [
{
"range": [
{
"introduced": "3.0.0.0"
},
{
"fixed": "3.2.1.0"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:o:siemens:simatic_itc1900_pro_firmware:*:*:*:*:*:*:*:*"
],
"vendor_product": "siemens:simatic_itc1900_pro_firmware",
"extracted_events": [
{
"range": [
{
"introduced": "3.0.0.0"
},
{
"fixed": "3.2.1.0"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:o:siemens:simatic_itc2200_firmware:*:*:*:*:*:*:*:*"
],
"vendor_product": "siemens:simatic_itc2200_firmware",
"extracted_events": [
{
"range": [
{
"introduced": "3.0.0.0"
},
{
"fixed": "3.2.1.0"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:o:siemens:simatic_itc2200_pro_firmware:*:*:*:*:*:*:*:*"
],
"vendor_product": "siemens:simatic_itc2200_pro_firmware",
"extracted_events": [
{
"range": [
{
"introduced": "3.0.0.0"
},
{
"fixed": "3.2.1.0"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*",
"cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:esm:*:*:*",
"cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*",
"cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*",
"cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*",
"cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*"
],
"vendor_product": "canonical:ubuntu_linux",
"extracted_events": [
{
"range": [
{
"introduced": "14.04"
},
{
"last_affected": "14.04"
},
{
"introduced": "16.04"
},
{
"last_affected": "16.04"
},
{
"introduced": "16.04"
},
{
"last_affected": "16.04"
},
{
"introduced": "18.04"
},
{
"last_affected": "18.04"
},
{
"introduced": "18.10"
},
{
"last_affected": "18.10"
},
{
"introduced": "20.04"
},
{
"last_affected": "20.04"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*",
"cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*"
],
"vendor_product": "debian:debian_linux",
"extracted_events": [
{
"range": [
{
"introduced": "8.0"
},
{
"last_affected": "8.0"
},
{
"introduced": "9.0"
},
{
"last_affected": "9.0"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*"
],
"vendor_product": "opensuse:leap",
"extracted_events": [
{
"range": [
{
"introduced": "15.2"
},
{
"last_affected": "15.2"
}
],
"source": "CPE_STRING"
}
]
}
]
}
},
"related_cves": [
{
"value": "CVE-2019-20840",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 387978,
"published_at": "2020-06-17T16:15:11.523+00:00"
}