MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePack-CSharp's typeless deserialization includes MessagePackSerializerOptions.ThrowIfDeserializingTypeIsDisallowed(Type) as a safety check for dangerous types. The default implementation checks the outer type name, but it does not recursively inspect array element types or generic type arguments. As a result, a type that would be blocked directly can be wrapped inside an array or constructed generic type and pass the outer type check. The formatter machinery can then materialize formatters for the inner blocked type. This vulnerability is fixed in 2.5.301 and 3.1.7.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-48517
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 6 Nov 2026, 01:20 UTC · Revision 1
Source evidence
MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments
core-osv · Original sourcePublished 22 Jun 2026, 21:03 UTC
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePack-CSharp's typeless deserialization includes MessagePackSerializerOptions.ThrowIfDeserializingTypeIsDisallowed(Type) as a safety check for dangerous types. The default implementation checks the outer type name, but it does not recursively inspect array element types or generic type arguments. As a result, a type that would be blocked directly can be wrapped inside an array or constructed generic type and pass the outer type check. The formatter machinery can then materialize formatters for the inner blocked type. This vulnerability is fixed in 2.5.301 and 3.1.7.
osv:CVE-2026-48517
Complete source record
{
"id": "c0c4d487ef1734a422dbef010b228b11a8d2d72eb3320df8fbe8752da90ab458",
"url": "https://osv.dev/vulnerability/CVE-2026-48517",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments",
"summary": "MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePack-CSharp's typeless deserialization includes MessagePackSerializerOptions.ThrowIfDeserializingTypeIsDisallowed(Type) as a safety check for dangerous types. The default implementation checks the outer type name, but it does not recursively inspect array element types or generic type arguments. As a result, a type that would be blocked directly can be wrapped inside an array or constructed generic type and pass the outer type check. The formatter machinery can then materialize formatters for the inner blocked type. This vulnerability is fixed in 2.5.301 and 3.1.7.",
"evidence": "osv:CVE-2026-48517",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2026-48517",
"aliases": [
"CVE-2026-48517",
"GHSA-qhmf-xw27-6rqr"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/messagepack-csharp/messagepack-csharp",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "5657b1e34ea2869a2ca6bc0aa6617158620201ba"
},
{
"introduced": "ff3af77f546138d9da71707baddf2c30f55dfc15"
},
{
"fixed": "1b53ae8b7681340199faf337bcbb0eb5aed702de"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\\#:*:*",
"range": [
{
"introduced": "0"
},
{
"fixed": "2.5.301"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\\#:*:*",
"range": [
{
"introduced": "3.0.3"
},
{
"fixed": "3.1.7"
}
],
"source": "CPE_RANGE"
}
]
}
}
],
"versions": [
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"v3.1.5",
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"v1.7.3.4",
"v1.7.3.3",
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"v1.7.3",
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"v1.7.0",
"v1.6.2",
"v1.6.1.2",
"v1.6.1",
"v1.6.0",
"v1.5.1",
"v1.5.0",
"v1.4.4",
"v1.4.2",
"v1.4.1",
"v1.4.0",
"v1.3.3",
"v1.3.2",
"v1.3.1",
"v1.3.0",
"v1.2.3",
"v1.2.1",
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"v1.1.2",
"v1.1.1",
"v1.0.3",
"v1.0.2",
"1.0.1",
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],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-48517.json"
}
}
],
"modified": "2026-10-28T02:30:45.515569284Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48517.json",
"https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-qhmf-xw27-6rqr",
"https://nvd.nist.gov/vuln/detail/CVE-2026-48517"
],
"provider_metadata": {
"cwe_ids": [
"CWE-470",
"CWE-502"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48517.json"
}
},
"related_cves": [
{
"value": "CVE-2026-48517",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 513793,
"published_at": "2026-06-22T21:03:30.437+00:00"
}