Quick answers
- Is CVE-2026-56416 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-56416 being exploited in the wild.
- How severe is CVE-2026-56416?
- Medium severity, with a CVSS score of 4.8, published 22 July 2026.
- Which products and versions are affected?
- NLnet Labs Unbound up to and including 1.25.1.
- Is there a fix for CVE-2026-56416?
- A patch was published on 2026-07-22: Fixed in version 1.25.2 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-56416 attacked?
- It is attacked over the network, in a hosted service.
- Am I affected by CVE-2026-56416?
- Check whether you run NLnet Labs Unbound at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A heap buffer overflow exists in Unbound's DNSSEC validator when processing RRSIG-covered RRsets for PX, RP, MINFO, or SOA records. The root cause is a failure to verify the presence of a second embedded domain name in the RDATA before passing a calculated pointer to 'query_dname_tolower()'. An attacker operating a DNSSEC-signed authoritative server can provide a truncated record that causes the parser to read past the intended buffer into stale bytes or beyond the heap allocation. This is particularly exploitable if 'msg-buffer-size' is configured below the default value. The issue is resolved in Unbound version 1.25.2.
Affected products
- NLnet Labs Unbound up to and including 1.25.1
Timeline
- 2026-07-22: disclosed
- 2026-07-22: advisory
- 2026-07-22: patched: Fixed in version 1.25.2