A flaw was found in nbdkit due to to improperly caching plaintext state across the STARTTLS encryption boundary. A MitM attacker could use this flaw to inject a plaintext NBDOPTSTRUCTURED_REPLY before proxying everything else a client sends to the server, potentially leading the client to terminate the NBD session. The highest threat from this vulnerability is to system availability.
{
"unresolved_ranges": [
{
"vendor_product": "redhat:enterprise_linux",
"extracted_events": [
{
"last_affected": "8.0"
},
{
"last_affected": "8.0"
}
],
"cpes": [
"cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:-:*:*:*",
"cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:advanced_virtualization:*:*:*"
],
"source": "CPE_STRING"
}
]
}{
"extracted_events": [
{
"introduced": "1.11.8"
},
{
"fixed": "1.24.6"
},
{
"introduced": "1.25.1"
},
{
"fixed": "1.26.5"
},
{
"introduced": "1.27.1"
},
{
"fixed": "1.27.6"
}
],
"cpe": "cpe:2.3:a:nbdkit_project:nbdkit:*:*:*:*:*:*:*:*",
"source": [
"CPE_RANGE",
"REFERENCES"
]
}"2026-05-30T17:27:46Z"
[
{
"digest": {
"line_hashes": [
"17736055569549823576078601167558441071",
"252569956524523289579052347941166243611",
"297470718666234456831894338929195417055"
],
"threshold": 0.9
},
"signature_version": "v1",
"id": "CVE-2021-3716-07c259cd",
"signature_type": "Line",
"deprecated": false,
"target": {
"file": "server/protocol-handshake-newstyle.c"
},
"source": "https://gitlab.com/nbdkit/nbdkit@09a13dafb7bb3a38ab52eb5501cba786365ba7fd"
},
{
"digest": {
"function_hash": "278656485481587851966178619826305884851",
"length": 9714.0
},
"signature_version": "v1",
"id": "CVE-2021-3716-72881b3f",
"signature_type": "Function",
"deprecated": false,
"target": {
"file": "server/protocol-handshake-newstyle.c",
"function": "negotiate_handshake_newstyle_options"
},
"source": "https://gitlab.com/nbdkit/nbdkit@09a13dafb7bb3a38ab52eb5501cba786365ba7fd"
}
]
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2021-3716.json"