CVE-2026-56416 Affecting unbound package, versions *


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.12% (2nd percentile)

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  • Snyk IDSNYK-ECHOLATEST-UNBOUND-18234997
  • published23 Jul 2026
  • disclosed22 Jul 2026

Introduced: 22 Jul 2026

NewCVE-2026-56416  (opens in a new tab)

How to fix?

There is no fixed version for Echo:latest unbound.

NVD Description

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

In NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain name as 'datstart + dname_valid(datstart, ...)' and passes it straight to 'query_dname_tolower()' without checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server can deliver a record with an absent second domain name (e.g. SOA record) and cause 'query_dname_tolower()' to walk label-by-label through stale bytes in the per-worker 'env->scratch_buffer', past the end of that heap allocation if 'msg-buffer-size' has been lowered from the default. This leads to heap buffer overflow and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap chunk.

CVSS Base Scores

version 3.1