CVE-2026-56416

Published: Lug 22, 2026 Last Modified: Lug 24, 2026
ExploitDB:
Other exploit source:
Google Dorks:
MEDIUM 4,8
Source: [email protected]
Attack Vector: network
Attack Complexity: high
Privileges Required: none
User Interaction: none
Scope: unchanged
Confidentiality: none
Integrity: low
Availability: low

Description

AI Translation Available

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.

354

Improper Validation of Integrity Check Value

Draft
Abstraction: Base Structure: Simple
Common Consequences
Security Scopes Affected:
Integrity Other Non-Repudiation
Potential Impacts:
Modify Application Data Other Hide Activities
Applicable Platforms
All platforms may be affected
Likelihood of Exploit: Medium
View CWE Details
Application

Unbound by Nlnetlabs

Product Information
Vendor Nlnetlabs
Product Unbound
Version Range Affected
To 1.25.2 (exclusive)
cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*
Common Platform Enumeration - Standardized vulnerability identification
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-56416.t…
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-56416.txt