CVE-2026-56416

MEDIUMPre-NVD 4.84.8—
EchelonGraph scoreHIGH confidence

Score 4.8 from GitHub Security Advisory published 2026-07-22. a secondary CVSS source baseline 4.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — Patch released this week
4.8EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 4.8Exploit: None knownExposed: 0

A fix is available — apply it.

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 v3
4.8
EG Score
4.8(high)
EG Risk
22(Track)
EG Risk 22/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity48% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
2%
KEV
Not listed

Published

July 22, 2026

Last Modified

July 24, 2026

Advisory Details (1)

Auto-updated Jul 22, 2026
No patch confirmed yet.
generic
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-56416.txt

Vendor Advisories for CVE-2026-56416(3)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatunbound-main-1.25.2-0.1.hum12026-07-22redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 17× in last 7d / 17× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-27 01:53 UTCEG score recompute
  2. 2026-07-27 01:53 UTCVendor advisory
  3. 2026-07-27 01:53 UTCGHSA enrichment
  4. 2026-07-26 03:28 UTCEG score recompute
  5. 2026-07-26 03:28 UTCVendor advisory
  6. 2026-07-26 03:28 UTCGHSA enrichment
  7. 2026-07-25 14:18 UTCEPSS rescore
  8. 2026-07-24 14:18 UTCEPSS rescore
  9. 2026-07-23 14:18 UTCEPSS rescore
  10. 2026-07-23 03:20 UTCEG score recompute
  11. 2026-07-22 22:01 UTCEG score recompute
  12. 2026-07-22 22:00 UTCGHSA enrichment
  13. 2026-07-22 17:13 UTCEG score recompute
  14. 2026-07-22 17:13 UTCGHSA enrichment
  15. 2026-07-22 14:55 UTCEG score recompute
  16. 2026-07-22 13:17 UTCEG score recompute
  17. 2026-07-22 13:17 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-56416?
CVE-2026-56416 is a medium vulnerability published on July 22, 2026. 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 + dnamevalid(datstart, ...)' and passes it straight to…
When was CVE-2026-56416 disclosed?
CVE-2026-56416 was first published in the National Vulnerability Database on July 22, 2026, with the most recent update on July 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-56416 actively exploited?
CVE-2026-56416 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 98.0% of all scored CVEs.
What is the CVSS score of CVE-2026-56416?
CVE-2026-56416 has a CVSS v3 base score of 4.8 (NVD).
How do I remediate CVE-2026-56416?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-56416, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-56416

Explore →

Is Your Infrastructure Affected by CVE-2026-56416?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs