Integer Overflow or Wraparound Affecting unbound-dracut package, versions *


Severity

Recommended
0.0
medium
0
10

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.25% (16th percentile)

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  • Snyk IDSNYK-RHEL10-UNBOUNDDRACUT-18339476
  • published28 Jul 2026
  • disclosed22 Jul 2026

Introduced: 22 Jul 2026

NewCVE-2026-55991  (opens in a new tab)
CWE-190  (opens in a new tab)

How to fix?

There is no fixed version for RHEL:10 unbound-dracut.

NVD Description

Note: Versions mentioned in the description apply only to the upstream unbound-dracut package and not the unbound-dracut package as distributed by RHEL. See How to fix? for RHEL:10 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1