DEBIAN-CVE-2026-55991
In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, a remote unauthenticated client can trigger a libngtcp2 assertion (if compiled with assertions on) and terminate the entire Unbound process using a single DNS-over-QUIC (DoQ) connection and one normal DNS query. This is caused by an erroneous error value passed to libngtcp2. When 'ngtcp2_conn_writev_stream()' returns 'NGTCP2_ERR_STREAM_DATA_BLOCKED', Unbound continues to call 'ngtcp2_ccerr_set_application_error()' with a '-1' error value. The 'int' literal '-1' is implicitly converted to the function's 'uint64_t error_code' parameter as '0xFFFFFFFFFFFFFFFF'. The follow-on 'ngtcp2_conn_write_connection_close()' serialises that value as a QUIC variable-length integer; because '2^64-1' exceeds the 62-bit varint ceiling, 'ngtcp2_put_uvarintlen()' fails 'assert(n < 4611686018427387904ULL)' and the whole resolver process aborts. A remote, unauthenticated DoQ client can trigger this deterministically with a single QUIC connection by advertising 'initial_max_stream_data_bidi_local = 1' in its transport parameters and sending one DoQ query without ever reading the stream.
DEBIAN-CVE-2026-55991
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:DEBIAN-CVE-2026-55991
unbound
Source reference: /affected/0/package/name
- Affected versions
- 1.17.1-2
Source reference:
/affected/0/versions1.17.1-2+deb12u1Source reference:
/affected/0/versions1.17.1-2+deb12u2Source reference:
/affected/0/versions1.17.1-2+deb12u3Source reference:
/affected/0/versions1.17.1-2+deb12u4Source reference:
/affected/0/versions1.17.1-2+loong64Source reference:
/affected/0/versions1.18.0-1Source reference:
/affected/0/versions1.18.0-2Source reference:
/affected/0/versions1.19.1-1Source reference:
/affected/0/versions1.19.2-1Source reference:
/affected/0/versions1.20.0-1Source reference:
/affected/0/versions1.21.1-1Source reference:
/affected/0/versions1.22.0-1Source reference:
/affected/0/versions1.22.0-2Source reference:
/affected/0/versions1.23.1-1Source reference:
/affected/0/versions1.24.0-1Source reference:
/affected/0/versions1.24.0-2Source reference:
/affected/0/versions1.24.1-1Source reference:
/affected/0/versions1.24.1-2Source reference:
/affected/0/versions1.24.2-1Source reference:
/affected/0/versions1.25.0-1Source reference:
/affected/0/versions1.25.1-1Source reference:
/affected/0/versions1.25.2-1Source reference:
/affected/0/versions1.26.0-1Source reference:
/affected/0/versions1.26.0-2Source reference:
/affected/0/versions1.26.1-1Source reference:
/affected/0/versions1.26.2-1Source reference:
/affected/0/versions - Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
unbound
Source reference: /affected/1/package/name
- Affected versions
- 1.22.0-2
Source reference:
/affected/1/versions1.22.0-2+deb13u1Source reference:
/affected/1/versions1.22.0-2+deb13u2Source reference:
/affected/1/versions1.22.0-2+deb13u3Source reference:
/affected/1/versions1.23.1-1Source reference:
/affected/1/versions1.24.0-1Source reference:
/affected/1/versions1.24.0-2Source reference:
/affected/1/versions1.24.1-1Source reference:
/affected/1/versions1.24.1-2Source reference:
/affected/1/versions1.24.2-1Source reference:
/affected/1/versions1.25.0-1Source reference:
/affected/1/versions1.25.1-1Source reference:
/affected/1/versions1.25.2-1Source reference:
/affected/1/versions1.26.0-1Source reference:
/affected/1/versions1.26.0-2Source reference:
/affected/1/versions - Fixed versions
- 1.26.1-0+deb13u1
Source reference:
/affected/1/ranges - Prerequisites
- Not stated in this record
unbound
Source reference: /affected/2/package/name
- Affected versions
- 1.22.0-2
Source reference:
/affected/2/versions1.23.1-1Source reference:
/affected/2/versions1.24.0-1Source reference:
/affected/2/versions1.24.0-2Source reference:
/affected/2/versions1.24.1-1Source reference:
/affected/2/versions1.24.1-2Source reference:
/affected/2/versions1.24.2-1Source reference:
/affected/2/versions1.25.0-1Source reference:
/affected/2/versions1.25.1-1Source reference:
/affected/2/versions - Fixed versions
- 1.25.2-1
Source reference:
/affected/2/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "unbound",
"purl": "pkg:deb/debian/unbound?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
"1.17.1-2",
"1.17.1-2+deb12u1",
"1.17.1-2+deb12u2",
"1.17.1-2+deb12u3",
"1.17.1-2+deb12u4",
"1.17.1-2+loong64",
"1.18.0-1",
"1.18.0-2",
"1.19.1-1",
"1.19.2-1",
"1.20.0-1",
"1.21.1-1",
"1.22.0-1",
"1.22.0-2",
"1.23.1-1",
"1.24.0-1",
"1.24.0-2",
"1.24.1-1",
"1.24.1-2",
"1.24.2-1",
"1.25.0-1",
"1.25.1-1",
"1.25.2-1",
"1.26.0-1",
"1.26.0-2",
"1.26.1-1",
"1.26.2-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55991.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.26.1-0+deb13u1"
}
]
}
],
"package": {
"name": "unbound",
"purl": "pkg:deb/debian/unbound?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"1.22.0-2",
"1.22.0-2+deb13u1",
"1.22.0-2+deb13u2",
"1.22.0-2+deb13u3",
"1.23.1-1",
"1.24.0-1",
"1.24.0-2",
"1.24.1-1",
"1.24.1-2",
"1.24.2-1",
"1.25.0-1",
"1.25.1-1",
"1.25.2-1",
"1.26.0-1",
"1.26.0-2"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55991.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.25.2-1"
}
]
}
],
"package": {
"name": "unbound",
"purl": "pkg:deb/debian/unbound?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"1.22.0-2",
"1.23.1-1",
"1.24.0-1",
"1.24.0-2",
"1.24.1-1",
"1.24.1-2",
"1.24.2-1",
"1.25.0-1",
"1.25.1-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55991.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
]Publisher severity
No explicit severity was provided.
- Event
- #57877 · Revision 1
- Added to Heist Feed
- Publisher date