Answer in brief
CVE-2026-42959 records a High severity (CVSS 8.7) vulnerability in Crash during DNSSEC validation of malicious content. The current sources do not mark it as known exploited. The current feed maps Red Hat/openshift/ose-rhel-coreos-9 (generic), Red Hat/unbound (generic), NLnet Labs/Unbound (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Red Hat/openshift/ose-rhel-coreos-9 (generic), Red Hat/unbound (generic), NLnet Labs/Unbound (generic). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| Red Hat/openshift/ose-rhel-coreos-9generic | * | Not reported |
| Red Hat/unboundgeneric | * | Not reported |
| NLnet Labs/Unboundgeneric | >=0 <1.25.1 | 1.25.1 |
Published upstream
May 20, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 1, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 15, 2026
NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.
Quoted source text, attributed separately from HOL analysis.